tty: Fix merge of "tty: Refactor tty_open()"

Commit e9036d06 ("tty: Drop krefs for interrupted tty lock")
fixed a tty reference counting problem introduced in
commit 0bfd464d ("tty: Wait interruptibly for tty lock on reopen"),
so v4.5.0 is correct.

However, commit d6203d0c ("tty: Refactor tty_open()") moved the
relevant code for 4.6-rc1; correct the merge.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_io.c

@@ -2049,14 +2049,13 @@ static struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode,
 	if (tty) {
 		mutex_unlock(&tty_mutex);
 		retval = tty_lock_interruptible(tty);
+		tty_kref_put(tty);  /* drop kref from tty_driver_lookup_tty() */
 		if (retval) {
 			if (retval == -EINTR)
 				retval = -ERESTARTSYS;
 			tty = ERR_PTR(retval);
 			goto out;
 		}
-		/* safe to drop the kref from tty_driver_lookup_tty() */
-		tty_kref_put(tty);
 		retval = tty_reopen(tty);
 		if (retval < 0) {
 			tty_unlock(tty);