[media] vivid: add the Test Pattern Generator

The test patterns for video capture are generated by this code. All patterns
are precalculated taking into account colorspace information, pixel and video
aspect ratios and scaling information.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>