mtd: rawnand: jz4740: 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 MACH_JZ4740 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

@@ -490,7 +490,8 @@ config MTD_NAND_NUC900
 
 config MTD_NAND_JZ4740
 	tristate "Support for JZ4740 SoC NAND controller"
-	depends on MACH_JZ4740
+	depends on MACH_JZ4740 || COMPILE_TEST
+	depends on HAS_IOMEM
 	help
 	  Enables support for NAND Flash on JZ4740 SoC based boards.