Revert "Removed unused file include/hardware/bt_gatt_types.h"

Revert submission 1402170
Bug: 165329887
Reason for revert: Breaking target docs on branch git_qt-qpr1-dev-plus-aosp
Reverted Changes:
Ifc81bd221:Unused def include/hardware/bt_gatt_types::btgatt_...
I59785ec5a:Removed unused file include/hardware/bt_gatt_types...

Change-Id: I41b9ac4ffae51adb0b62599320a5a568eaf81b36