extmod/nimble: Enable key distribution to support bonding.

This sets the BLE key distribution parameters at runtime. This isn't
needed in most ports since we already set the default values in
`extmod/nimble/syscfg/syscfg.h`; however in the ESP32 port that
headerfile is not used, and the default values in the ESP-IDF don't
enable key distribution nor can we change those defaults via
`sdkconfig`. Thus we're setting these values explicitly at runtime.

Signed-off-by: Daniël van de Giessen <[email protected]>

Author: DvdGiessen

extmod/nimble/modbluetooth_nimble.c

@@ -617,6 +617,8 @@ int mp_bluetooth_init(void) {
     ble_hs_cfg.store_status_cb = ble_store_util_status_rr;
 
     #if MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING
+    ble_hs_cfg.sm_our_key_dist = BLE_SM_PAIR_KEY_DIST_ENC | BLE_SM_PAIR_KEY_DIST_ID | BLE_SM_PAIR_KEY_DIST_SIGN;
+    ble_hs_cfg.sm_their_key_dist = BLE_SM_PAIR_KEY_DIST_ENC | BLE_SM_PAIR_KEY_DIST_ID | BLE_SM_PAIR_KEY_DIST_SIGN;
     ble_hs_cfg.store_read_cb = ble_secret_store_read;
     ble_hs_cfg.store_write_cb = ble_secret_store_write;
     ble_hs_cfg.store_delete_cb = ble_secret_store_delete;