drm: omapdrm: Pass drm_device to omap_gem_resume()

The omap_gem_resume() function is internal to the driver. Pass it a
drm_device pointer that the caller already has instead of looking it up
from device data.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>