xfs: free up mp->m_free[0].count in error case

In xfs_init_percpu_counters(), memory for mp->m_free[0].count wasn't freed
in error case. Free it up in this patch.

Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Fixes: 712bae96 ("xfs: generalize the freespace and reserved blocks handling")
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>