hal: reset backend configuration before speaker calibration

For speaker thermal calibration, backend needs to be configured
with default sample rate(48kHz). Currently backend configuration
does not reset to default value after playback finishes, results
in failure of speaker calibration. Fix this issue by resetting the
backend configuration to default primary output value before
speaker thermal calibration.

Change-Id: Id231faf7249506ef668a943b6b12c2738b504a50