This config option is for the USB OTG pin, pin A10. This is used on
some boards but not others. Eg PYBv3 uses PA10 for LED(2), so it
shouldn't be used for OTG ID (actually PA10 is multiplexed on this
board, but defaults to LED(2)).
Partially addresses issue #1059.
Pulled in and modified work done by mux/iabdalkader on cc3k driver, from
iabdalkader-cc3k-update branch. That branch was terribly messy and had
too many conflicts to merge neatly.
