Staging: lustre: mark a variable static in workitem.c

This fixes a sparse warning:
warning: symbol 'cfs_wi_data' was not declared. Should it be static?
Signed-off-by: Mike Sampson <mike@sambodata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/libcfs/workitem.c

@@ -75,7 +75,7 @@ typedef struct cfs_wi_sched {
 	char			ws_name[CFS_WS_NAME_LEN];
 } cfs_wi_sched_t;
 
-struct cfs_workitem_data {
+static struct cfs_workitem_data {
 	/** serialize */
 	spinlock_t		wi_glock;
 	/** list of all schedulers */