mx25: move ARCH_MXC_IOMUX_V3 to the ARCH level

ARCH_MXC_IOMUX_V3 is not specific to the i.MX25 PDK platform. Thus,
ARCH_MXC_IOMUX_V3 should be selected by ARCH_MX25.
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx25/Kconfig

@@ -3,7 +3,6 @@ if ARCH_MX25
 comment "MX25 platforms:"
 
 config MACH_MX25_3DS
-	select ARCH_MXC_IOMUX_V3
 	bool "Support MX25PDK (3DS) Platform"
 
 endif

arch/arm/plat-mxc/Kconfig

@@ -24,6 +24,7 @@ config ARCH_MX25
 	bool "MX25-based"
 	select CPU_ARM926T
 	select COMMON_CLKDEV
+	select ARCH_MXC_IOMUX_V3
 	select HAVE_FB_IMX
 	help
 	  This enables support for systems based on the Freescale i.MX25 family