ASoC: msm8996: dynamically detect wsa881x parts in target

MSM8996 target might have varying number of wsa881x parts.
The machine driver should be capable of figuring out how
many wsa881x parts are present and accordingly register
those as part of sound card.

Change-Id: Ic36e752ccf3e68f27d21517422d35b71525eee8b
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>