spl: nand: add support for mxs nand

spl: nand: add support for mxs nand

This utilizes existing mxs_nand support layer to provide a method to load an
image off nand for SPL. The flash device will be detected in order to support
multiple flash devices instead of having layout hard coded at build time.

Cc: Stefan Roese <[email protected]>
Cc: Otavio Salvador <[email protected]>
Cc: Andy Ng <[email protected]>
Cc: Eric Nelson <[email protected]>
Cc: Tapani Utriainen <[email protected]>
Cc: Tom Rini <[email protected]>
Cc: Scott Wood <[email protected]>
Signed-off-by: Tim Harvey <[email protected]>