SPL: P1022DS: fix the problem booting from spi flash

There was no enough memory for malloc in SPL booting from spi flash, so
relayout the memory in SPL: reduce the memory for global data from 16K
Bytes to 4K Bytes, save the space for malloc.

Signed-off-by: Ying Zhang <b40530@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>