vt: add missing notification when switching back to text mode

[ Upstream commit ff78538 ]

Programs using poll() on /dev/vcsa to be notified when VT changes occur
were missing one case: the switch from gfx to text mode.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Link: https://lore.kernel.org/r/9o5ro928-0pp4-05rq-70p4-ro385n21n723@onlyvoer.pbz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: npitre

drivers/tty/vt/vt.c

@@ -4452,6 +4452,7 @@ void do_unblank_screen(int leaving_gfx)
 	set_palette(vc);
 	set_cursor(vc);
 	vt_event_post(VT_EVENT_UNBLANK, vc->vc_num, vc->vc_num);
+	notify_update(vc);
 }
 EXPORT_SYMBOL(do_unblank_screen);