clk: mmp: fix sparse non static symbol warning

Fixes the following sparse warnings:

drivers/clk/mmp/clk-frac.c:113:6: warning:
 symbol 'clk_factor_init' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Michael Turquette <mturquette@linaro.org>

drivers/clk/mmp/clk-frac.c

@@ -110,7 +110,7 @@ static int clk_factor_set_rate(struct clk_hw *hw, unsigned long drate,
 	return 0;
 }
 
-void clk_factor_init(struct clk_hw *hw)
+static void clk_factor_init(struct clk_hw *hw)
 {
 	struct mmp_clk_factor *factor = to_clk_factor(hw);
 	struct mmp_clk_factor_masks *masks = factor->masks;