msm: ASoC: Implement local call hold

Add support for local call hold in voice driver. In multi
subscription scenario, when a call is recieved on one subscription
while a call is already active on another subscription, then active
call will be put on local call hold.

Change-Id: Ie409797e2dd4faf1f53251a3b150a56b2bee9f42
Signed-off-by: Shiv Maliyappanahalli <smaliyap@codeaurora.org>