target: msm8909: update backlight MPP for 8909 with PM8916

8909 devices with PM8916 use MPP4 for backlight while the
regular 8909 devices use MPP2. Add the change to take care
of the same using device subtype.

Change-Id: Ia0f0a81f71bc5a7b6bd0b8463ec8f7fa448cbe64
1 file changed