staging: lustre: osc: Remove remains of osc_ast_guard

osc_ast_guard has been removed by the clio simplification.
Remove the last lock class definition.
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7148
Reviewed-on: http://review.whamcloud.com/16392Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/osc/osc_dev.c

@@ -94,8 +94,6 @@ struct lu_kmem_descr osc_caches[] = {
 	}
 };
 
-struct lock_class_key osc_ast_guard_class;
-
 /*****************************************************************************
  *
  * Type conversions.

drivers/staging/lustre/lustre/osc/osc_request.c

@@ -2845,7 +2845,6 @@ static struct obd_ops osc_obd_ops = {
 };
 
 extern struct lu_kmem_descr osc_caches[];
-extern struct lock_class_key osc_ast_guard_class;
 
 static int __init osc_init(void)
 {