ASoC: msm: qdsp6v2: Add support for HFP on MSM8996

BT Hands Free Profile(HFP) uses primary AUXPCM interface on
MSM8996. Add support for Primary AUXPCM loopback volume mixer
and update existing mixer get/put function names for Secondary
AUXPCM to reflect port specific names.

Change-Id: I18bd72d3afff815b3183df822cc1da7065ce1799
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>