clk: rockchip: make clk_half_divider_ops static

The clk_half_divider_ops is not used outside or declared
outside of drivers/clk/rockchip/clk-half-divider.c so make
it static to avoid the following warning:

drivers/clk/rockchip/clk-half-divider.c:142:22: warning: symbol 'clk_half_divider_ops' was not declared. Should it be static?

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20191017105348.8061-1-ben.dooks@codethink.co.uk
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

drivers/clk/rockchip/clk-half-divider.c

@@ -139,12 +139,11 @@ static int clk_half_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 	return 0;
 }
 
-const struct clk_ops clk_half_divider_ops = {
+static const struct clk_ops clk_half_divider_ops = {
 	.recalc_rate = clk_half_divider_recalc_rate,
 	.round_rate = clk_half_divider_round_rate,
 	.set_rate = clk_half_divider_set_rate,
 };
-EXPORT_SYMBOL_GPL(clk_half_divider_ops);
 
 /**
  * Register a clock branch.