ARM: dts: msm: allow VDD_GFX CPR open-loop aging adjustment for msm8996pro

Allow the VDD_GFX CPR open-loop voltage to be adjusted based
upon aging measurements.  This ensures that the closed-loop
voltage has room to increase as necessary.

Change-Id: I7ae8a4f90628f36f5e6164d18a4457552a20a8a1
CRs-Fixed: 949622
Signed-off-by: David Collins <collinsd@codeaurora.org>