LU-9633 ptlrpc: Add kernel doc style for ptlrpc (9)

LU-9633 ptlrpc: Add kernel doc style for ptlrpc (9)

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: I94c5b18dca250d0279b85b92019f34f5e67ce6b5
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/59518
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>