staging: dgap: remove "return" statement in void function

clean up checkpatch warning:
WARNING: void function return statements are not generally useful
Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgap/dgap.c

@@ -3077,8 +3077,6 @@ static void dgap_tty_send_xchar(struct tty_struct *tty, char c)
 
 	spin_unlock_irqrestore(&ch->ch_lock, lock_flags2);
 	spin_unlock_irqrestore(&bd->bd_lock, lock_flags);
-
-	return;
 }
 
 /*