The GFX_MODE is reset along with the engine, turning off ppGTT. We need
to re-enable it upon resume afterwards.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210114101451.24762-1-chris@chris-wilson.co.uk