V4L/DVB (11744): pvrusb2: Select, track, and report IR scheme in use with the device

This change defines all possible "IR schemes" related to the pvrusb2
driver, on a per-device basis.  That information is then set according
to the hardware in use.  The idea here is to make possible a more
intelligent future decision on which, if any, IR receiver driver might
be loaded during initialization.

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