ASoC: msm8x10: Add support for Voice2

Add front-end DAI Voice2 to enable a second voice path in the DSP
for calls from the second modem.

Change-Id: I6223a5319ebd42450395e7f047a9c82a78be5b9d
Signed-off-by: Helen Zeng <xiaoyunz@codeaurora.org>