Bluetooth: Support  HFP Client role on Bluedroid.

Implementation changes to support HFP Client role
on Bluedroid stack.

Change-Id: Id020db2a5dd63a4fe5cb7b500a7a39b3027c4913
(cherry picked from commit 05588448988ee28f22bd00884f5a43b69c2b95b8)
(cherry picked from commit 4e428790cef944280bf250e9b22a54f7ef88ad24)
(cherry picked from commit a3ceffd8df3e5552b2250106c2b7f4fcdc4c71be)