LU-9633 ptlrpc: Add kernel doc style for ptlrpc (7)

LU-9633 ptlrpc: Add kernel doc style for ptlrpc (7)

This patch converts existing functional comments
to kernel doc style comments and removes '/**' for
comments which is not meant to be a kernel-doc comment

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I21532bbcb07b00dfb6275f5cd25015b46564c745
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58863
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Marc Vef <mvef@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>