xfs: fix an error code in xfs_fs_fill_super()

If alloc_percpu() fails, we accidentally return PTR_ERR(NULL), which
means success, but we intended to return -ENOMEM.

Fixes: 225e4635 ('xfs: per-filesystem stats in sysfs')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_super.c

@@ -1477,7 +1477,7 @@ xfs_fs_fill_super(
 	/* Allocate stats memory before we do operations that might use it */
 	mp->m_stats.xs_stats = alloc_percpu(struct xfsstats);
 	if (!mp->m_stats.xs_stats) {
-		error = PTR_ERR(mp->m_stats.xs_stats);
+		error = -ENOMEM;
 		goto out_destroy_counters;
 	}