drm/mgag200: Extract device type from flags

drm/mgag200: Extract device type from flags

Adds a conversion function that extracts the device type from the
PCI id-table flags. Allows for storing additional information in the
other flag bits.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 81da87f63a1e ("drm: Replace drm_gem_vram_push_to_system() with kunmap + unpin")
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: John Donnelly <john.p.donnelly@oracle.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: "Y.C. Chen" <yc_chen@aspeedtech.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: "José Roberto de Souza" <jose.souza@intel.com>
Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.3+
Link: https://patchwork.freedesktop.org/patch/msgid/20191126101529.20356-2-tzimmermann@suse.de