[media] pwc: Simplify leds parameter parsing

This reduces our module init to a simple usb_register() call, so
that we can make use of the new upcoming macro's for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>