mtd: rawnand: omap2: Prevent invalid configuration and build error

We need to select MEMORY as well otherwise OMAP_GPMC will not be built.
For simplicity let's select MEMORY and OMAP_GPMC unconditionally as
this driver depends on OMAP_GPMC driver and uses symbols from there.

Fixes: dbcb124a

 ("mtd: rawnand: omap2: Select GPMC device driver for ARCH_K3")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220118123525.8020-1-rogerq@kernel.org