V4L/DVB (4664): Pvrusb2: Don't use videodev.h; use v4l2-dev.h in its place

The function prototype needed in pvrusb2-v4l2.c has been moved to
v4l2-dev.h.  Track that change.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>