staging: lustre: uapi: label lustre_ioctl.h as a UAPI header

staging: lustre: uapi: label lustre_ioctl.h as a UAPI header

Change LUSTRE_IOCTL_H_ to _UAPI_LUSTRE_IOCTL_H_ now that is
a proper UAPI header

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6401
Reviewed-on: https://review.whamcloud.com/24568
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>