drm/msm: add max-freq gpu param to uapi

We need this in userspace for interpreting some of the perf ctrs.

Note possibly not quite sufficient if we had some frequency mgmt
approach other than race-to-idle.  Not really sure what the best
thing to do if we did.  Although displaying results as a percentage
of max frequence seems sensible(ish) if we did.

Change-Id: Ic0dedbad1d8481cd2609ae0d86d4de6045f0d22e
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Git-commit: 4102a9e5325941223fbfa0a56175e9efb3d4385a
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>