Fix init sequence for BT AV sink.

BTA_AvEnable_Sink() was being called to early causing
a crash loop when the BT AV_SINK was included. This patch
changes up the init sequence to match that of the av
source. Also, rename a few constants for clarity.

Change-Id: I3e6a7e22a2643eeceb4afc082979d1d9967b0b99
3 files changed