BluetoothAudioHAL: Supports the A2dpSuspended parameter

When establishing a SCO connection, HFP will use the A2dpSuspended
parameter to inform audio HALs for preventing A2DP playback and SCO
coexistence. Since some Bluetooth headset could not handle both A2DP
streaming and SCO at the same time but became abnormal, usually APPs who
was going to use SCO should first acquire the audio focus to pause the
A2DP playback, and then asked for SCO. Because some APPs did not do so,
we need this change to help preventing such IOPs.

Bug: 138698886
Bug: 144820778
Test: make A2DP and SCO connections manually
Change-Id: Id9a1ad08908b30055e02c12a671fc02537ac7100