[media] tpg: Export the tpg code from vivid as a module

The test pattern generator will be used by other drivers as the virtual
media controller (vimc)

Signed-off-by: Helen Mae Koike Fornazier <helen.koike@collabora.co.uk>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>