drm/ttm: Add common debugfs code for resource managers

drm/ttm: Add common debugfs code for resource managers

Drivers duplicate the code required to add debugfs entries for various
ttm resource managers. To fix it add common TTM resource manager debugfs
code that each driver can reuse.

Specific resource managers can overwrite
ttm_resource_manager_func::debug to get more information from those
debugfs entries.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220412033526.369115-2-zack@kde.org
Reviewed-by: Christian König <christian.koenig@amd.com>