LU-9243 gss: fix GSS struct definition badness

LU-9243 gss: fix GSS struct definition badness

struct lgssd_ioctl_param should not be defined in multiple places. So
move it to a new header file lgss.h that can be included from kernel
space and user space.

struct gss_header, struct gss_rep_header, struct gss_err_header and
struct gss_wire_ctx are going on the wire, so they need to be moved to
lustre_idl.h, and be wire-checked.

Lustre-change: https://review.whamcloud.com/46543
Lustre-commit: 7dfbc71350c982be20d75e7d7853038809f4e850

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I97c4a8322e6bb7627c6dff5f068931278f4567d7
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/47667
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>