drivers/misc: ti-st: Remove unneeded variable in st_tty_open

st_tty_open do not need local variable to store different value,
Hence just remove it.
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Link: https://lore.kernel.org/r/1568307147-43468-1-git-send-email-zhongjiang@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/ti-st/st_core.c

@@ -708,7 +708,6 @@ EXPORT_SYMBOL_GPL(st_unregister);
  */
 static int st_tty_open(struct tty_struct *tty)
 {
-	int err = 0;
 	struct st_data_s *st_gdata;
 	pr_info("%s ", __func__);
 
@@ -731,7 +730,8 @@ static int st_tty_open(struct tty_struct *tty)
 	 */
 	st_kim_complete(st_gdata->kim_data);
 	pr_debug("done %s", __func__);
-	return err;
+
+	return 0;
 }
 
 static void st_tty_close(struct tty_struct *tty)