clk: mxs: Fix sparse warnings

Fix the following sparse warnings:

drivers/clk/mxs/clk.c:17:1: warning: symbol 'mxs_lock' was not declared. Should it be static?
drivers/clk/mxs/clk.c:19:5: warning: symbol 'mxs_clk_wait' was not declared. Should it be static?

Signed-off-by: Fabio Estevam <[e-mail]>
Acked-by: Shawn Guo <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

drivers/clk/mxs/clk.c

···
 #include <linux/io.h>
 #include <linux/jiffies.h>
 #include <linux/spinlock.h>
+#include "clk.h"
 
 DEFINE_SPINLOCK(mxs_lock);