drm/msm: Add param for userspace to query suspend count

Performance counts, and ALWAYS_ON counters used for capturing GPU
timestamps, lose their state across suspend/resume cycles.  Userspace
tooling for performance monitoring needs to be aware of this.  For
example, after a suspend userspace needs to recalibrate it's offset
between CPU and GPU time.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Acked-by: Jordan Crouse <jordan@cosmicpenguin.net>
Link: https://lore.kernel.org/r/20210325012358.1759770-3-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>