ARM: mxs: support full SPL framework

This allows using the full SPL framework on mxs devices. In this
mode, the u-boot.sb image loaded by the boot ROM contains only the
SPL which then loads U-Boot proper or a kernel in falcon mode.

Signed-off-by: Mans Rullgard <mans@mansr.com>

ARM: mxs: support full SPL framework

This allows using the full SPL framework on mxs devices. In this
mode, the u-boot.sb image loaded by the boot ROM contains only the
SPL which then loads U-Boot proper or a kernel in falcon mode.

Signed-off-by: Mans Rullgard <mans@mansr.com>