media: media/v4l2-core/videobuf-vmalloc.c: Remove dead code

This code is commented since version 3.7. If there is no plan to
use it in future, we can remove this dead code.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>