V4L/DVB (6773): pvrusb2: rework device descriptor layout

The pvrusb2 driver tries to keep all device specific attributes in a
single data structure in one source file.  This change further cleans
up how that table is set up.  We now try to group everything together
for each specific device, and the number of symbols exported from this
module has now been reduced to a single global.

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