ASoC: msm: Add I2S support for MDM9x15.

Add changes to enable I2S interface for MDM9x15.
Interface detection between slimbus and I2S is
done at codec init. Driver and functions for that
interface are called during routing. Proper amix
controls for the interface should be used.

Change-Id: I18a8ffab0d2fcdfebf460435eb81e8dacc38e25b
Signed-off-by: Venkat Sudhir <vsudhir@codeaurora.org>