extmod/btstack: Add stub functions for passkey, l2cap bindings.
extmod/btstack: Add stub functions for passkey, l2cap bindings.

Signed-off-by: Damien George <99e6b749acbfbe2a596df99e91d24d6e1fdbee00@micropython.org>

henriknelson/micropython,adafruit/circuitpython,adafruit/circuitpython,henriknelson/micropython,henriknelson/micropython,bvernoux/micropython,bvernoux/micropython,bvernoux/micropython,henriknelson/micropython,adafruit/circuitpython,adafruit/circuitpython,bvernoux/micropython,adafruit/circuitpython,bvernoux/micropython,adafruit/circuitpython,henriknelson/micropython