arm/imx: let ARCH_MXC select COMMON_CLKDEV instead of each subfamily

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 233a222..39baa60 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -312,6 +312,7 @@
 	select GENERIC_GPIO
 	select ARCH_REQUIRE_GPIOLIB
 	select HAVE_CLK
+	select COMMON_CLKDEV
 	help
 	  Support for Freescale MXC/iMX-based family of processors