OneNAND: Add simple OneNAND SPL

OneNAND: Add simple OneNAND SPL

This introduces small OneNAND loader, fitting into 1kB of space (smallest
possible OneNAND RAM size). Some devices equipped with such crappy chips will
use this.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Albert ARIBAUD <[email protected]>
Cc: Kyungmin Park <[email protected]>
Cc: Scott Wood <[email protected]>
V2: Introduce spl_onenand_load_image() to load data from OneNAND in SPL
V3: Cleanup, align with nand_spl. Skip whole blocks.