mtd: rawnand: atmel: Defer probe if SRAM is missing

mtd: rawnand: atmel: Defer probe if SRAM is missing

The Atmel NAND controller driver depends on an SRAM pool and has an
implicit assumption that the SRAM pool has already been created.
Changing the initcall ordering can break this. Unfortunately, fw_devlink
can't save us here as there's not a standard property to track the
dependency. So it's up to deferring probe to save us.

Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>