pxa3xx_nand: update dependancy to support ARCH_MMP

MTD_NAND_PXA3xx module is shared between ARCH_PXA and ARCH_MMP. Update
this configuration according to it.
Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>

drivers/mtd/nand/Kconfig

@@ -358,7 +358,7 @@ endchoice
 
 config MTD_NAND_PXA3xx
 	tristate "Support for NAND flash devices on PXA3xx"
-	depends on MTD_NAND && PXA3xx
+	depends on MTD_NAND && (PXA3xx || ARCH_MMP)
 	help
 	  This enables the driver for the NAND flash device found on
 	  PXA3xx processors