Properly expose the mfu ghost list kstats

Due to a typo the mru ghost lists stats were accidentally being
exposed as the mfu ghost list stats.  This was harmless but
confusing since memory usage could be over reported.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

module/zfs/arc.c

@@ -3708,7 +3708,7 @@ arc_kstat_update(kstat_t *ksp, int rw)
 		    &as->arcstat_mfu_size,
 		    &as->arcstat_mfu_evict_data,
 		    &as->arcstat_mfu_evict_metadata);
-		arc_kstat_update_state(arc_mru_ghost,
+		arc_kstat_update_state(arc_mfu_ghost,
 		    &as->arcstat_mfu_ghost_size,
 		    &as->arcstat_mfu_ghost_evict_data,
 		    &as->arcstat_mfu_ghost_evict_metadata);