xfs: avoid the iolock in xfs_free_eofblocks for evicted inodes

Same rational as the last patch - these inodes are not reachable, so
don't bother with locking.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Rich Johnston <rjohnston@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>