Add get_gatt_db to Bluetooth HAL

This patch adds new method, get_gatt_db to bluetooth HAL.
It can be used to grab whole GATT database in one request.
It will trigger get_gatt_db_callback, which is also part of
this patch.

Change-Id: I1a931f126db56e7a29537f3bca9cddff3dd27dc6
2 files changed