ARM: mach-imx: clk: Include "clk.h"

Fix the following sparse warning:

arch/arm/mach-imx/clk.c:3:1: warning: symbol 'imx_ccm_lock' 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-imx/clk.c

 #include <linux/spinlock.h>
+#include "clk.h"
 
 DEFINE_SPINLOCK(imx_ccm_lock);