tty/vt: Return EBUSY if deallocating VT1 and it is busy

Commit 421b40a6286e ("tty/vt: Fix vc_deallocate() lock order") changed
the behavior when deallocating VT 1. Previously if trying to
deallocate VT1 and it is busy, we would return EBUSY. The commit
changed this to return 0 (success).

This commit restores the old behavior.

Signed-off-by: Ross Lagerwall <[e-mail]>
Tested-by: Mikael Pettersson <[e-mail]>
Acked-by: Peter Hurley <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/vt/vt_ioctl.c

···
 	struct vc_data *vc = NULL;
 	int ret = 0;
 
-	if (!vc_num)
-		return 0;
-
 	console_lock();
 	if (VT_BUSY(vc_num))
 		ret = -EBUSY;
-	else
+	else if (vc_num)
 		vc = vc_deallocate(vc_num);
 	console_unlock();