ARM: dts: msm: Correct GPU IB vote on MSM8917

Currently GPU IB vote is 2X times the required IB vote
for a particular DDR frequency level. This is causing
DDR to run at higher clock.

This change corrects the GPU IB vote to keep DDR clock
at required level.

Change-Id: I4faaceb99f9194dd4218dff1b881843d48d0e604
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>