drm/amd/amdgpu: Fold TTM debugfs entries into array (v2)

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

(v2): add domains and avoid strcmp