vt: add missing notification when switching back to text mode

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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/vt/vt.c

···
 	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);