LU-6142 lnet: Fix style issues for list.h

LU-6142 lnet: Fix style issues for list.h

This patch fixes issues reported by checkpatch
for both files libcfs/include/libcfs/util/list.h

Update inline doc to kernel-doc style

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Ic8bef64aa24d079b2242ec9ac63ee7b38726f714
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56306
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>