Revert "Unused def include/hardware/bt_gatt_types::btgatt_transp..."

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: Ie89181741bad772b14d722ff0cb6823fc9c71860