drm/ttm/memcg/lru: enable memcg tracking for ttm and amdgpu driver (complete series v2)

[Dave Airlie]

Hi all,

This is a repost with some fixes and cleanups.

Differences since last posting:
1. Added patch 18: add a module option to allow pooled pages to not be stored in the lru per-memcg
   (Requested by Christian Konig)
2. Converged the naming and stats between vmstat and memcg (Suggested by Shakeel Butt)
3. Cleaned up the charge/uncharge code and some other bits.

Dave.

Original cover letter:
tl;dr: start using list_lru/numa/memcg in GPU driver core and amdgpu driver for now.

This is a complete series of patches, some of which have been sent before and reviewed,
but I want to get the complete picture for others, and try to figure out how best to land this.

There are 3 pieces to this:
01->02: add support for global gpu stat counters (previously posted, patch 2 is newer)
03->07: port ttm pools to list_lru for numa awareness
08->14: add memcg stats + gpu apis, then port ttm pools to memcg aware list_lru and shrinker
15->17: enable amdgpu to use new functionality.

The biggest difference in the memcg code from previously is I discovered what
obj cgroups were designed for and I'm reusing the page/objcg intergration that 
already exists, to avoid reinventing that wheel right now.

There are some igt-gpu-tools tests I've written at:
https://gitlab.freedesktop.org/airlied/igt-gpu-tools/-/tree/amdgpu-cgroups?ref_type=heads

One problem is there are a lot of delayed action, that probably means the testing
needs a bit more robustness, but the tests validate all the basic paths.

Regards,
Dave.