V4L/DVB (10490): v4l2: prefill ident and revision from v4l2_dbg_chip_ident.

Drivers that implement this always have to set the ident and revision
to V4L2_IDENT_NONE and 0. Do this in the v4l2 core so drivers don't have
to do this.

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