drm/i915: suspend fbdev device around suspend/hibernate

Looking at hibernate overwriting I though it looked like a cursor,
so I tracked down this missing piece to stop the cursor blink
timer. I've no idea if this is sufficient to fix the hibernate
problems people are seeing, but please test it.

Both radeon and nouveau have done this for a long time.

I've run this personally all night hib/resume cycles with no fails.

Reviewed-by: Keith Packard <keithp@keithp.com>
Reported-by: Petr Tesarik <kernel@tesarici.cz>
Reported-by: Stanislaw Gruszka <sgruszka@redhat.com>
Reported-by: Lots of misc segfaults after hibernate across the world.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=37142
Tested-by: Dave Airlie <airlied@redhat.com>
Tested-by: Bojan Smojver <bojan@rexursive.com>
Tested-by: Andreas Hartmann <andihartmann@01019freenet.de>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>