[media] bw-qcam: fix timestamp handling

bw-qcam didn't set the timestamp and it didn't set q->timestamp_type.

Tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>