SystemUI: fix zen mode panel warning not showing

We need to request a relayout of the view so the panel has a chance to
pick up the new height and update to that size.

Ref: CYNGNOS-2063

Change-Id: I6fa95f7a5a72646e0a990b6ffbac51fffdcf5272
Signed-off-by: Roman Birg <roman@cyngn.com>