[media] pvrusb2: Don't use module names to load I2C modules

[media] pvrusb2: Don't use module names to load I2C modules

With the v4l2_i2c_new_subdev* functions now supporting loading modules
based on modaliases, replace the hardcoded module name passed to those
functions by NULL.

All corresponding I2C modules have been checked, and all of them include
a module aliases table with names corresponding to what the pvrusb2
driver uses.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-By: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>