[media] media: ti-vpe: Use line average de-interlacing for first 2 frames

The motion detection block requires 3 fields to create the motion vector
data. This means that using the default method the first progressive
frame is only generated after 3rd field is consumed.
Hence by default for N input field we would generate N - 2 progressive
frames.

In order to generate N progressive frames from N fields we use the
line averaging mode of the de-interlacer for the first 2 fields and then
revert back to the preferred Edge Directed Interpolation method (using
the motion vector).
Thus creating 2 line averaged frames + N - 2 motion based frames for a
total of N frames.

Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Nikhil Devshatwar <nikhil.nd@ti.com>
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>