[media] media: davinci: vpif_display: drop unused member fbuffers

As fbuffers is not used anymore, remove it.
No functional changes.

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>