xfs_reserve_blocks() calls xfs_icsb_sync_counters_locked(), which is not
defined if !CONFIG_SMP/!HAVE_PERCPU_SB

SGI-PV: 976035
SGI-Modid: xfs-linux-melb:xfs-kern:30991a
Signed-off-by: NEric Sandeen <sandeen@sandeen.net>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>