overclocking: initial MSM S4-pro overclocking to 1.836 GHz

Signed-off-by: Paul Reioux <reioux@gmail.com>
WIP: drm/msm: spin helper
WIP: drm/msm: crank down gpu when inactive
HACK: overclock gpu to 487.5MHz
WIP: drm/msm: add chip-id param

Some of the w/a or different behavior of userspace blob driver seem to
be keyed to gpu patch revision, rather than gpu-id.