hal: Remove the sleep time to restart output if disconnecting bt-a2dp

The 50ms sleep time only is needed for card offline,it is unnecessary
when switching device from bt-a2dp to other device, which will cause
that remaining PCM data can't get drained and volume bursts can be heard.

Remove the sleep time to restart output when switching device from
bt-a2dp.

CRs-fixed: 2626614
Change-Id: I768619a5a1b6d7a995c41551566bead8861da37f