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

With the v4l2_i2c_new_subdev* functions now supporting loading modules
based on modaliases, don't use the module names hardcoded in platform
data by passing a NULL module name to those functions.

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

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>