[MTD] Make XIP support depend on CONFIG_ARM

ARM is the only known user of this at the moment.
Prevent allyes builds for other archs from failing

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/drivers/mtd/chips/Kconfig b/drivers/mtd/chips/Kconfig
index b5dc593..df95d21 100644
--- a/drivers/mtd/chips/Kconfig
+++ b/drivers/mtd/chips/Kconfig
@@ -300,7 +300,7 @@
 
 config MTD_XIP
 	bool "XIP aware MTD support"
-	depends on !SMP && (MTD_CFI_INTELEXT || MTD_CFI_AMDSTD) && EXPERIMENTAL
+	depends on !SMP && (MTD_CFI_INTELEXT || MTD_CFI_AMDSTD) && EXPERIMENTAL && ARM
 	default y if XIP_KERNEL
 	help
 	  This allows MTD support to work with flash memory which is also