media: platform: ti: avoid using 'videobuf' or 'video-buf'

These terms typically refer to the old version 1 videobuf framework.
It is confusing to use them for the vb2 framework, so reword these
comments.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Lad Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>