V4L/DVB (7780): pvrusb2: always enable support for OnAir Creator / HDTV USB2

This was a build option in the past, to avoid conflicts with the cxusb module
for digital televsion support.  Now that dtv mode support has been merged into
pvrusb2, the OnAir devices are fully supported by this single module.  This no
longer should be a build option.

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