um: Fix time-travel mode

Since the time-travel rework, basic time-travel mode hasn't worked
properly, but there's no longer a need for this WARN_ON() so just
remove it and thereby fix things.

Cc: stable@vger.kernel.org
Fixes: 4b786e2 ("um: time-travel: Rewrite as an event scheduler")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/kernel/time.c

@@ -260,11 +260,6 @@ static void __time_travel_add_event(struct time_travel_event *e,
 	struct time_travel_event *tmp;
 	bool inserted = false;
 
-	if (WARN(time_travel_mode == TT_MODE_BASIC &&
-		 e != &time_travel_timer_event,
-		 "only timer events can be handled in basic mode"))
-		return;
-
 	if (e->pending)
 		return;