call ble_gap_event_listener_call for every ble_gap_notify_tx_event
call ble_gap_event_listener_call for every ble_gap_notify_tx_event

Needed to get the notification transmitted event with a listener
registered by ble_gap_event_listener_register to be able to chain
ble notifications.
If there are two different modules on different application levels
and both are using nimble, then it is not possible for the
lower-level module to register a "feature-complete" callback via
ble_gap_adv_start, because this function should only be called
by the higher-level module, because it knows, when the application
is ready for advertising.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble