[media] davinci vpbe: OSD(On Screen Display) block

This patch implements the functionality of the OSD block
of the VPBE. The OSD in total supports 4 planes or Video
sources - 2 mainly RGB and 2 Video. The patch implements general
handling of all the planes, with specific emphasis on the Video
plane capabilities as the Video planes are supported through the
V4L2 driver.

Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Acked-by: Muralidharan Karicheri <m-karicheri2@ti.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>