ASoC: MSM8974: Add device tree binding

Update machine driver to be a platform driver in order to support
device tree binding. This change would allow easy swapping of DAPM
routes, sound card name, board specific settings for various MSM8974
based form factors.

Change-Id: I892227834e4149c80737e5b12872c266ff46484d
Signed-off-by: Kiran Kandi <kkandi@codeaurora.org>