V4L/DVB (10258): pvrusb2: Issue VIDIOC_INT_INIT to v4l2 modules when they first attach

It appears that various v4l-dvb drivers are changing to require
explicit initialization before use.  This change to the pvrusb2 driver
implements an automatic issuance of VIDIOC_INT_INIT when a module is
bound to the driver, thus conforming to the new behavior.

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