ASoC: msm8996: add support for dynamic wsa881x detection

Add support in machine driver to be able to parse device
tree for all possible wsa881x that are supported in the
target, find out from ALSA core about how many wsa881x out
of the list of devices passed from device tree are present
in the target and already registered with ALSA as codec,
and eventually register those wsa881x devices (which are
present) as AUX codec to be used with the sound card.

Change-Id: I09e80772fad2a141862c04d31a00324ce6ea98f8
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>