Add an xfs_icsb_balance_counter_locked for the case where mp->m_sb_lock is
already locked.

SGI-PV: 976035
SGI-Modid: xfs-linux-melb:xfs-kern:30918a
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>