mtd: rawnand: txx9ndfmc: 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 SOC_TX4938 or SOC_TX4939
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>
Acked-by: Paul Burton <paul.burton@mips.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/raw/Kconfig

@@ -469,7 +469,8 @@ config MTD_NAND_DAVINCI
 
 config MTD_NAND_TXX9NDFMC
 	tristate "NAND Flash support for TXx9 SoC"
-	depends on SOC_TX4938 || SOC_TX4939
+	depends on SOC_TX4938 || SOC_TX4939 || COMPILE_TEST
+	depends on HAS_IOMEM
 	help
 	  This enables the NAND flash controller on the TXx9 SoCs.