drm/amdgpu: Add cgroups implementation

Similar to xe, enable some simple management of VRAM only.

Reviewed-by: Christian König <christian.koenig@amd.com>
Co-developed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>