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

Commit 421b40a ("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 <rosslagerwall@gmail.com>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Acked-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/vt/vt_ioctl.c

@@ -289,13 +289,10 @@ static int vt_disallocate(unsigned int vc_num)
 	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();