LU-11025 mdt: remove unused code

LU-11025 mdt: remove unused code

Remove obsolete code in dir_split_count_store() which are left in
code rebase.

Test-parameters: trivial

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Id72385307623c7f281ea855e4c02fe110f1ed235
Reviewed-on: https://review.whamcloud.com/38801
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>