drm/ttm: enable TTM page pool kerneldoc

Fix the remaining warnings and finally enable this.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210908132933.3269-9-christian.koenig@amd.com
2 files changed