ARM: mxs: pm: Include "pm.h"

Fix the following sparse warning:

arch/arm/mach-mxs/pm.c:37:13: warning: symbol 'mxs_pm_init' was not declared. Should it be static?
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

arch/arm/mach-mxs/pm.c

@@ -15,6 +15,7 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include "pm.h"
 
 static int mxs_suspend_enter(suspend_state_t state)
 {