LU-8191 ptlrpc: convert functions to static

LU-8191 ptlrpc: convert functions to static

Static analysis shows that a number of functions
could be made static. This patch declares several
functions in ptlrpc static.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: If0d92f7f4e625c146833f360806ae80b8914cc20
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51353
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>