nand_spl_simple: Add a simple NAND read function

nand_spl_simple: Add a simple NAND read function

To support UBI in SPL we need a simple NAND read function. Add one to
nand_spl_simple and keep it as simple as it goes.

Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Ladislav Michl <[email protected]>
Acked-by: Scott Wood <[email protected]>
Reviewed-by: Tom Rini <[email protected]>
Reviewed-by: Heiko Schocher <[email protected]>