ASoC: codecs: Add msm8916-wcd digital codec

msm8916-wcd codec is found in Qualcomm msm8916 and apq8016 processors.
This codec IP is split in to two parts(Digital & Analog).
Analog part is integrated in to PMIC PM8916 and the digital part is
integrated into Application processor. Data transfer between Analog and
Digital Die is done via a internal bus called PDM.

This patch adds support to Digital part of the Codec which is integrated
into Application Processor.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>