ARM: dts: msm: add PDM i2s enable switch

Since the GPIO 88 switch enable is no longer
specific only to the TDM board, add another
switch enable for the PDM microphones.

Change-Id: I4f8a2e641878fec3501c47c3b6c7b42d9cdd894d
Signed-off-by: Kenneth Westfield <kwestfie@codeaurora.org>