ARM: dts: msm: Add support for GPU AB vote on SDM845

Add qcom,bus-width property required to support AB
bus voting for GPU on SDM845 and also correct the
IB vote table to reduce the vote to half because
SDM845 DDR configuration is 4x16 channel.

Change-Id: I893404ff1c469675963e43d03b3535e748c23851
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>