[media] pvrusb2: fix missing device_caps in querycap

The VIDIOC_QUERYCAP function should set device_caps, but this was missing.
In addition, it set the version field as well, but that should be done by
the core, not by the driver.

If a driver doesn't set device_caps the v4l2 core will issue a WARN_ON, so
it's important that this is set correctly.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>