drm/qxl: Use TTM builtin resource manager debugfs code

Switch to using the TTM resource manager debugfs helpers. The
functionality is largely the same.
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: Dave Airlie <airlied@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: virtualization@lists.linux-foundation.org
Cc: spice-devel@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220412033526.369115-5-zack@kde.org


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