powerpc/t104xrdb: support deep sleep in SPI/SD boot

Add deep sleep support in SPI/SD boot. The destination address
second stage uboot image is loaded to is changed because
currently this address will be used by kernel which means
we can't reserve it for resume.

Entry point to kernel is still placed in second stage uboot.

Signed-off-by: Tang Yuantian <Yuantian.Tang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>