libalsa-intf: Fix for no audio on specific USB device

- Playback volume is not initialized for USB device due to this
  on some specific headsets no audio heard even if we increase
  the playback volume to maximum.
- Fix is to explicitly initialize the volume for USB headset
  before starting the playback using mixer control. As USB
  driver supports DB_MINMAX for volume control add support
  for same in alsa_mixer.

Change-Id: Icaa5e0072ce95439418c61d60aed819ac98b3f63
CRs-Fixed: 478906