Staging: dgnc: release the lock before testing for nullity

The refactoring intrduced in
c84a083b ("Staging: dgnc: Use goto for spinlock release before return")
inverts the order in which the lock is released and ld is tested for nullity.

This patch restores the execution flow.

Fixes: c84a083b ("Staging: dgnc: Use goto for spinlock release before return")
Signed-off-by: NQuentin Lambert <lambert.quentin@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgnc/dgnc_tty.c

@@ -656,9 +656,9 @@ void dgnc_input(struct channel_t *ch)
 	return;
 
 exit_unlock:
+	spin_unlock_irqrestore(&ch->ch_lock, flags);
 	if (ld)
 		tty_ldisc_deref(ld);
-	spin_unlock_irqrestore(&ch->ch_lock, flags);
 }