This fixes two problems with the BTstack implementation of descriptor
discovery:
- The call to gatt_client_discover_characteristic_descriptors needs to have
value_handle set to the starting handle (actually characteristic handle)
to start the search from.
- The BTstack event for a descriptor query result is
GATT_EVENT_ALL_CHARACTERISTIC_DESCRIPTORS_QUERY_RESULT.
With this change the test tests/multi_bluetooth/ble_subscribe.py now passes
when BTstack is instance1 (for BTstack to pass as instance0 requires
gatts_write to support sending an update on BTstack).
Signed-off-by: Damien George <damien@micropython.org>
bdad63eda2