board/p1_p2_rdb:Enable p1_p2_rdb boot from NAND/SD/SPI in SPL

board/p1_p2_rdb:Enable p1_p2_rdb boot from NAND/SD/SPI in SPL

In the earlier patches, the SPL/TPL fraamework was introduced.
For SD/SPI flash booting way, we introduce the SPL to enable a loader stub. The
SPL was loaded by the code from the internal on-chip ROM. The SPL initializes
the DDR according to the SPD and loads the final uboot image into DDR, then
jump to the DDR to begin execution.

For NAND booting way, the nand SPL has size limitation on some board(e.g.
P1010RDB), it can not be more than 4KB, we can call it "minimal SPL", So the
dynamic DDR driver doesn't fit into this minimum SPL. We added the TPL that is
loaded by the the minimal SPL. The TPL initializes the DDR according to the SPD
and loads the final uboot image into DDR,then jump to the DDR to begin execution.

This patch enabled SPL/TPL for P1_P2_RDB to support starting from NAND/SD/SPI
flash with SPL framework and initializing the DDR according to SPD in the SPL/TPL.
Because the minimal SPL load the TPL to L2 SRAM and the jump to the L2 SRAM to
execute, so the section .resetvec is no longer needed.

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>