staging: lustre: lnet: change msg union in struct lnet_hdr to proper structure

staging: lustre: lnet: change msg union in struct lnet_hdr to proper structure

Modify all the msg union fields from typedefs to
to proper structures.

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6142
Reviewed-on: https://review.whamcloud.com/24566
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Olaf Weber <olaf@sgi.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>