drm/msm: Improved debugfs gem stats

The last patch lost the breakdown of active vs inactive GEM objects in
$debugfs/gem.  But we can add some better stats to summarize not just
active vs inactive, but also purgable/purged to make up for that.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20210401012722.527712-5-robdclark@gmail.com


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