hal: switch to current active device when a2dp suspended

When SCO profile is disabled, during voice call, device can be
switched to handset first and followed with a2dpsuspended param,
device will be switched to speaker and if it shares backend with
handset, voice call can be eventually switched to speaker which
is unexpected.
Check if there's any other active usecase and switch to the same
one during check_a2dp_restore.

Change-Id: I2cabccffc5d2601362a5da16b9793c218a009822