arm/imx: merge i.MX3 and i.MX6

The patch merges the build of imx3 and imx6.  The Kconfig symbol
ARCH_IMX_V6_V7 is introduced to replace ARCH_MX3 and ARCH_MX6.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 193439e..4e98937 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -158,9 +158,8 @@
 machine-$(CONFIG_ARCH_MSM)		:= msm
 machine-$(CONFIG_ARCH_MV78XX0)		:= mv78xx0
 machine-$(CONFIG_ARCH_IMX_V4_V5)	:= imx
-machine-$(CONFIG_ARCH_MX3)		:= imx
+machine-$(CONFIG_ARCH_IMX_V6_V7)	:= imx
 machine-$(CONFIG_ARCH_MX5)		:= mx5
-machine-$(CONFIG_ARCH_MX6)		:= imx
 machine-$(CONFIG_ARCH_MXS)		:= mxs
 machine-$(CONFIG_ARCH_NETX)		:= netx
 machine-$(CONFIG_ARCH_NOMADIK)		:= nomadik