V4L/DVB (13508): pms: source code cleanup, use struct v4l2_device.

This prepares the pms driver for the v4l1 -> v4l2 conversion.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>