powerpc/85xx:Fix IVORs addr after vector table relocation

After relocation of vector table in SDRAM's lower address, IVORs value should
be updated with new handler addresses.

As vector tables are relocated to 0x100,0x200... 0xf00 address in DDR.IVORs
are updated with 0x100, 0x200,....f00  hard-coded values.

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>