[XFS] Make freeze code a little cleaner.

Fixes a few small issues (mostly cosmetic) that were picked up during the
review cycle for the last set of freeze path changes.

SGI-PV: 959267
SGI-Modid: xfs-linux-melb:xfs-kern:28035a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tim Shimmin <tes@sgi.com>