ARM: dts: msm: enable closed-loop CPR operation for VDD_GFX on msm8996

Switch from open-loop (CPR disabled) to closed-loop (CPR enabled)
operation for VDD_GFX which powers the GPU.  This ensures that
additional power is saved.

Change-Id: I4fe3d1402f017b37ec0d492ed68d16cae71a09c2
Signed-off-by: David Collins <collinsd@codeaurora.org>