V4L/DVB (8901): pvrusb2: Disable virtual IR device when not needed.

Disable "virtual" IR receiver on for 24xxx devices that have an
internal IR blaster.  In that case there's another another IR
receiver present and to leave the virtual receiver available
just causes confusion.  This means that 24xxx users will no
longer see a phantom IR chip.

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