[MTD] [NAND] GPIO driver depends on ARM... for now.

Not all architectures provide readsb(). We should probably move to using
ioread8_rep() instead.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index b9eed99..1c2e945 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -58,7 +58,7 @@
 
 config MTD_NAND_GPIO
 	tristate "GPIO NAND Flash driver"
-	depends on GENERIC_GPIO
+	depends on GENERIC_GPIO && ARM
 	help
 	  This enables a GPIO based NAND flash driver.