clk: rockchip: Remove redundant null check before clk_prepare_enable

Because clk_prepare_enable() already checked NULL clock parameter,
so the additional check is unnecessary, just remove it.
Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20201127090551.50254-1-vulab@iscas.ac.cnSigned-off-by: Heiko Stuebner <heiko@sntech.de>

drivers/clk/rockchip/clk.c

@@ -603,8 +603,7 @@ void rockchip_clk_protect_critical(const char *const clocks[],
 	for (i = 0; i < nclocks; i++) {
 		struct clk *clk = __clk_lookup(clocks[i]);
 
-		if (clk)
-			clk_prepare_enable(clk);
+		clk_prepare_enable(clk);
 	}
 }
 EXPORT_SYMBOL_GPL(rockchip_clk_protect_critical);