bootvx: use program header for loading

bootvx: use program header for loading

The section header address is a VMA whereas the address found in
the program header is a physical one. With this change it is
possible to load and start a vx7 intel generic based image.

$ readelf -l /tmp/vx7

Elf file type is EXEC (Executable file)
Entry point 0x408000
There are 2 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x001000 0x00408000 0x00408000 0x04000 0x04000 RWE 0x1000
  LOAD           0x005000 0xe040c000 0x0040c000 0x583a84 0x5ccc70 RWE 0x1000

 Section to Segment mapping:
  Segment Sections...
   00     .text.locore .data.locore
   01     .text .eh_frame .wrs_build_vars .data .tls_data .tls_vars .bss

$ readelf -S /tmp/vx7
There are 13 section headers, starting at offset 0x588af8:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .text.locore      PROGBITS        00408000 001000 00011e 00  AX  0   0 16
  [ 2] .data.locore      PROGBITS        00409000 002000 003000 00  WA  0   0 4096
  [ 3] .text             PROGBITS        e040c000 005000 4802a0 00 WAX  0   0 32
  [ 4] .eh_frame         PROGBITS        e088c2a0 4852a0 0a1ed0 00   A  0   0  4
  [ 5] .wrs_build_vars   PROGBITS        e092e170 527170 000190 00  Ax  0   0  1
  [ 6] .data             PROGBITS        e092f000 528000 060a70 00  WA  0   0 4096
  [ 7] .tls_data         PROGBITS        e098fa70 588a70 000004 00   A  0   0  4
  [ 8] .tls_vars         PROGBITS        e098fa78 588a78 00000c 00  WA  0   0  4
  [ 9] .bss              NOBITS          e098faa0 588a84 0491d0 00  WA  0   0 32
  [10] .shstrtab         STRTAB          00000000 588a84 000074 00      0   0  1
  [11] .symtab           SYMTAB          00000000 588d00 056ee0 10     12 9758  4
  [12] .strtab           STRTAB          00000000 5dfbe0 05f48a 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

For completeness here are the same information for an old vx5 based image. After
this change it is possible to boot vx5 and vx7 (intel generic) images.

$ readelf -l /tmp/vx5

Elf file type is EXEC (Executable file)
Entry point 0x308000
There are 1 program headers, starting at offset 52

Program Headers:
 Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
 LOAD           0x000060 0x00308000 0x00308000 0x3513a0 0x757860 RWE 0x20

Section to Segment mapping:
 Segment Sections...
  00     .text .data .bss
[christian@chgm-pc ~]$ readelf -S /tmp/vx5
There are 12 section headers, starting at offset 0x356580:

Section Headers:
 [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
 [ 0]                   NULL            00000000 000000 000000 00      0   0  0
 [ 1] .text             PROGBITS        00308000 000060 319b10 00 WAX  0   0 32
 [ 2] .data             PROGBITS        00621b20 319b80 037880 00  WA  0   0 32
 [ 3] .bss              NOBITS          006593a0 351400 4064c0 00  WA  0   0 16
 [ 4] .debug_aranges    PROGBITS        00000000 351400 000060 00      0   0  1
 [ 5] .debug_pubnames   PROGBITS        00000000 351460 00018b 00      0   0  1
 [ 6] .debug_info       PROGBITS        00000000 3515eb 003429 00      0   0  1
 [ 7] .debug_abbrev     PROGBITS        00000000 354a14 000454 00      0   0  1
 [ 8] .debug_line       PROGBITS        00000000 354e68 0016a4 00      0   0  1
 [ 9] .shstrtab         STRTAB          00000000 35650c 000071 00      0   0  1
 [10] .symtab           SYMTAB          00000000 356760 0440e0 10     11 8574  4
 [11] .strtab           STRTAB          00000000 39a840 03e66c 00      0   0  1
Key to Flags:
 W (write), A (alloc), X (execute), M (merge), S (strings)
 I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
 O (extra OS processing required) o (OS specific), p (processor specific)

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>