audio_route: Add APIs to update mixer based on path

audio_route_apply_and_update_path
audio_route_reset_and_update_path

These routines allows updating the mixer controls for
just the specified path. The controls will be updated
in the order listed in the XML file.

Change-Id: If193bc047ccbb8c6497926d6181c5c4541a9d6aa
CRs-Fixed: 581453
Merge pull request #2 from omnirom/android-4.4

audio_route: Add APIs to update mixer based on path