LU-6142 mdd: Fix style issues for mdd_dir.c

LU-6142 mdd: Fix style issues for mdd_dir.c

This patch fixes issues reported by checkpatch
for file lustre/mdd/mdd_dir.c

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I255a2cfe2dd7c09ce421cb7c5387cef0bba73611
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54217
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>