hal: add a new key to query for decoder viability

- Due to resource constraints some times a decoder playback cannot
be supported, for example HW decoders cannot be supported during
voice calls, this key can be queried to know about this.

- Bring in the this funtionality in HAL under the android prop
"voice.playback.conc.disabled".

Change-Id: Id6819b1b953c8ba9948c85218d98beb789f92631
CRs-Fixed: 902360