drm/msm: Add param for the highest bank bit

This parameter is programmed by the kernel and influences the tiling
layout of images. Exposing it to userspace will allow it to tile/untile
images correctly without guessing what value the kernel programmed, and
allow us to change it in the future without breaking userspace.

Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/571181/


Signed-off-by: Rob Clark <robdclark@chromium.org>