ARM: imx: rename mach dir for mx21 and mx27 to mach-imx

Finally all imx code should end up there, start with mach-mx2.  While
touching all files rename some files to use a hyphen instead of an
underscore.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 64ba313..c60d604 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -146,7 +146,7 @@
 machine-$(CONFIG_ARCH_MSM)		:= msm
 machine-$(CONFIG_ARCH_MV78XX0)		:= mv78xx0
 machine-$(CONFIG_ARCH_MX1)		:= mx1
-machine-$(CONFIG_ARCH_MX2)		:= mx2
+machine-$(CONFIG_ARCH_MX2)		:= imx
 machine-$(CONFIG_ARCH_MX25)		:= mx25
 machine-$(CONFIG_ARCH_MX3)		:= mx3
 machine-$(CONFIG_ARCH_MX5)		:= mx5