Convert the samd port from the old `MICROPY_EVENT_POLL_HOOK` macro to use
the new `mp_event_wait_xxx()` functions in conjunction with
`MICROPY_INTERNAL_WFE`.
This change should be functionally equivalent to the existing behaivour
because `mp_event_wait_ms()` is equal to
`mp_handle_pending(MP_HANDLE_PENDING_CALLBACKS_AND_EXCEPTIONS); __WFE()`,
which is what `MICROPY_EVENT_POLL_HOOK` was.
Signed-off-by: Damien George <damien@micropython.org>
1f601e8987