aarch64: Add ARMv8 AARCH64 support files

aarch64: Add ARMv8 AARCH64 support files

Add new AARCH64 target and ARMv8 support files.
This is an instantiation from the cortex_a files but modified to support
64bit ARMv8. Not all features are complete, notably breakpts and single
stepping are not yet implemented.
Currently it lets you halt of the processors, resume, dump cpu
registers,
read/write memory and getting a stack trace with gdb.

> halt
invalid mode value encountered 5
target state: halted
unrecognized psr mode: 0x5
target halted in ARM state due to debug-request, current mode:
UNRECOGNIZED
cpsr: 0x600001c5 pc: 0x00093528
MMU: disabled, D-Cache: disabled, I-Cache: disabled

> targets
    TargetName         Type       Endian TapName            State
--  ------------------ ---------- ------ ------------------ ------------
 0* cpu0               aarch64    little cpu.dap            halted

> reg
===== arm v8 registers
(0) r0 (/64): 0x00000000FFFFFFED (dirty)
(1) r1 (/64): 0x00000000F76E4000
(2) r2 (/64): 0x0000000000000000
(3) r3 (/64): 0x0000000000010000
(4) r4 (/64): 0xFFFFFFC06E2939E1
(5) r5 (/64): 0x0000000000000018
(6) r6 (/64): 0x003A699CFB3C8480
(7) r7 (/64): 0x0000000053555555
(8) r8 (/64): 0x00FFFFFFFFFFFFFF
(9) r9 (/64): 0x000000001FFEF992
(10) r10 (/64): 0x0000000000000001
(11) r11 (/64): 0x0000000000000000
(12) r12 (/64): 0x00000000000000F0
(13) r13 (/64): 0x00000000EFDFEAC8
(14) r14 (/64): 0x00000000F6DDA659
(15) r15 (/64): 0x0000000000000000
(16) r16 (/64): 0xFFFFFFC0000F9094
(17) r17 (/64): 0x0000000000000000
(18) r18 (/64): 0x0000000000000000
(19) r19 (/64): 0xFFFFFFC00087C000
(20) r20 (/64): 0x0000000000000002
(21) r21 (/64): 0xFFFFFFC000867C28
(22) r22 (/64): 0xFFFFFFC000916A52
(23) r23 (/64): 0xFFFFFFC00116D8B0
(24) r24 (/64): 0xFFFFFFC000774A0C
(25) r25 (/64): 0x000000008007B000
(26) r26 (/64): 0x000000008007D000
(27) r27 (/64): 0xFFFFFFC000080450
(28) r28 (/64): 0x0000004080000000
(29) r29 (/64): 0xFFFFFFC00087FF20
(30) r30 (/64): 0xFFFFFFC000085114
(31) sp (/64): 0xFFFFFFC00087FF20
(32) pc (/64): 0xFFFFFFC000093528
(33) xPSR (/64): 0x00000000600001C5

And from gdb

(gdb) bt
 #0  cpu_do_idle () at /mnt/host/source/src/third_party/kernel/3.14/arch/arm64/mm/proc.S:87
 #1  0xffffffc000085114 in arch_cpu_idle () at /mnt/host/source/src/third_party/kernel/3.14/arch/arm64/kernel/process.c:107
 #2  0x0000000000000000 in ?? ()

Change-Id: Iccb1d15c7d8ace7b9e811dac3c9757ced4d0f618
Signed-off-by: David Ung <david.ung.42@gmail.com>
Signed-off-by: Matthias Welwarsky <matthias.welwarsky@sysgo.com>