mtd: rawnand: omap2: Allow selection of this driver when COMPILE_TEST=y

It just makes NAND maintainers' life easier by allowing them to
compile-test this driver without having ARCH_OMAP2PLUS or ARCH_KEYSTONE
enabled.

We also need to add a dependency on HAS_IOMEM to make sure the driver
compiles correctly.
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/raw/Kconfig

@@ -77,7 +77,8 @@ config MTD_NAND_AMS_DELTA
 
 config MTD_NAND_OMAP2
 	tristate "NAND Flash device on OMAP2, OMAP3, OMAP4 and Keystone"
-	depends on (ARCH_OMAP2PLUS || ARCH_KEYSTONE)
+	depends on ARCH_OMAP2PLUS || ARCH_KEYSTONE || COMPILE_TEST
+	depends on HAS_IOMEM
 	help
           Support for NAND flash on Texas Instruments OMAP2, OMAP3, OMAP4
 	  and Keystone platforms.