ARM: mxs: mm: Fix sparse warning

Include <mach/common.h> header to fix the following sparse warnings:

arch/arm/mach-mxs/mm.c:43:13: warning: symbol 'mx23_map_io' was not declared. Should it be static?
arch/arm/mach-mxs/mm.c:48:13: warning: symbol 'mx28_map_io' was not declared. Should it be static?
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-mxs/mm.c

@@ -18,6 +18,7 @@
 
 #include <mach/mx23.h>
 #include <mach/mx28.h>
+#include <mach/common.h>
 
 /*
  * Define the MX23 memory map.