extmod/modbluetooth: In gap_advertise only accept None to stop adv.
extmod/modbluetooth: In gap_advertise only accept None to stop adv.

To match the docs, and interval=0 may be used in the future to indicate
something else.

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython