clk: Deduplicate exit code in clk_set_rate

On non-out case 'return ret;' is equivalent to 'return 0;' as the ret
variable is initialized at 0 and never changed.
Signed-off-by: Nestor Ovroy <novroy@riseup.net>

drivers/clk/clk.c

@@ -1093,9 +1093,6 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
 	/* change the rates */
 	clk_change_rate(top);
 
-	mutex_unlock(&prepare_lock);
-
-	return 0;
 out:
 	mutex_unlock(&prepare_lock);