ARM: imx: mmdc: Include "common.h" header file

Include the "common.h" header file to fix the following sparse warning:

arch/arm/mach-imx/mmdc.c:66:5: warning: symbol 'imx_mmdc_get_ddr_type' 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-imx/mmdc.c

@@ -17,6 +17,8 @@
 #include <linux/of_address.h>
 #include <linux/of_device.h>
 
+#include "common.h"
+
 #define MMDC_MAPSR		0x404
 #define BP_MMDC_MAPSR_PSD	0
 #define BP_MMDC_MAPSR_PSS	4