PIO state machines can make a conditional jump on the state of a pin: the
`JMP PIN` command. This requires the pin to be configured with
`sm_config_set_jmp_pin`, but until now we didn't have a way of doing that
in MicroPython.
This commit adds a new `jmp_pin=None` argument to `StateMachine`. If it is
not `None` then we try to interpret it as a Pin, and pass its value to
`sm_config_set_jmp_pin`.
Signed-off-by: Tim Radvan <tim@tjvr.org>
7a9027fd5d