staging: lustre: Annotate user buffer with __user

Fix the warning reported by sparse on drivers/staging/lustre/lnet/lnet/router_proc.c
warning: incorrect type in argument 4 (different address spaces)
The correction is to annotate all user buffer variable by __user

Signed-off-by: LABBE Corentin <clabbe.montjoie@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>