drm/ttm: Remove unnecessary drm_mm_clean

Remove unnecessary `drm_mm_clean` calling in
`ttm_range_man_fini_nocheck`, due to effective
check is already included in the following
`drm_mm_takedown`.

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221012124735.1702700-1-zengheng4@huawei.com


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