f1 f3 usb: move usb_conf.h down into cpu-specific library

The f1 and f3 usb_conf.h file was incorrectly located under
the top-level pios inc directory.
usb: remove board-id from usb bcdDevice field for all OP boards

The board id was unnecessarily being encoded into the bcdDevice
field.  Nothing actually uses that value in that field so
having it there is just misleading.
f4 usb: make board-specific copies of usb_conf.h

The revolution and revomini f4 targets need a different
setup for usb_conf.h.  This is (currently) due to the
revo/revomini boards needing to disable the
   VBUS_SENSING_ENABLED
configuration since they don't connect VBUS to the dedicated
USB peripheral pins.

All boards now carry their own independent copy of this file
so that the conflicting requirements can be satisfied.
revo/revomini usb: always init the HID and CDC drivers

It is essential that both the HID and CDC drivers are always
initialized since the USB device descriptor advertises both
of these interfaces.  Any interface that is advertised can
have its callbacks called.  Failing to properly init the
class-specific drivers results in memory scribling and other
follow-on badness.