hal: fix output device selection when start voice call

When primary output device is set to A2DP, voice usecase
will select BT_A2DP for output device. This is not valid
device for voice call.

Fix it by add A2DP check to avoid voice call start at A2DP.

CRs-Fixed: 2227493
Change-Id: Iad5bda633f7ff2c456ae1a7b015845b37c5e1c39