drm/ttm: add ttm_resource_fini v2

Make sure we call the common cleanup function in all
implementations of the resource manager.

v2: fix missing case in i915, rudimentary kerneldoc, should be
    filled in more when we add more functionality

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220124122514.1832-2-christian.koenig@amd.com