drm/amdgpu: Use TTM builtin resource manager debugfs code

Switch to using the TTM resource manager debugfs helpers. It's
exactly the same functionality but the debugfs code is shared with
other drivers.

The TTM resource managers need to stay valid for as long as the
drm debugfs_root is valid.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Nirmoy Das <nirmoy.das@amd.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: amd-gfx@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220412033526.369115-4-zack@kde.org


Reviewed-by: Christian König <christian.koenig@amd.com>