clk: rockchip: don't return NULL when failing to register ddrclk branch

rockchip_clk_register_ddrclk should not return NULL when failing
to call clk_register, otherwise rockchip_clk_register_branches
prints "unknown clock type". The actual case is that it's a known
clock type but we fail to register it, which may makes user confuse
the reason of failure. And the pr_err here is pointless as
rockchip_clk_register_branches will also print the similar message.

Signed-off-by: Shawn Lin <[e-mail]>
Signed-off-by: Heiko Stuebner <[e-mail]>

drivers/clk/rockchip/clk-ddr.c

···
 	ddrclk->ddr_flag = ddr_flag;
 
 	clk = clk_register(NULL, &ddrclk->hw);
-	if (IS_ERR(clk)) {
-		pr_err("%s: could not register ddrclk %s\n", __func__,	name);
+	if (IS_ERR(clk))
 		kfree(ddrclk);
-		return NULL;
-	}
 
 	return clk;
 }