msm: board-8960-pmic: Add platform data for PWM driver

Add default platform data to enable DTEST configuration
for PM8921 LPG channels.
With the help of this feature, a given LPG channel can
be selected to drive the DTEST line.

Change-Id: I810ffac4a9498d9b8327ab503e3b067f04f4a873
Signed-off-by: Jay Chokshi <jchokshi@codeaurora.org>