V4L/DVB (5053): Pvrusb2: Change default volume to something sane

The default volume of 65535 is too high.  Make is something smaller.
Note that this _only_ changes the default value.  Specifically, there
are no scaling or other more intrusive changes here.  I'm just sick of
constantly having to reduce the volume every time I plug in and test
the device!  (And unfortunately we can't do a better fix like scaling
the volume so that 65535 makes sense because doing so will screw up
any app - like MythTV - which expects the old scaling.)  Too bad V4L
controls don't have better defined ranges.

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