Input: zforce - simplify function return logic

The invoked function already returns zero on success or a negative
errno code so there is no need to open code the logic in the caller.

This also fixes the following make coccicheck warning:

end returns can be simplified and declaration on line 602 can be dropped

Signed-off-by: Javier Martinez Canillas <[e-mail]>
Reviewed-by: Heiko Stuebner <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/touchscreen/zforce_ts.c

···
 static int zforce_input_open(struct input_dev *dev)
 {
 	struct zforce_ts *ts = input_get_drvdata(dev);
-	int ret;
 
-	ret = zforce_start(ts);
-	if (ret)
-		return ret;
-
-	return 0;
+	return zforce_start(ts);
 }
 
 static void zforce_input_close(struct input_dev *dev)