spinand: bind mtdblock

Bind SPI-NAND driver to MTD block driver.

Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>