xfs: reverse the polarity of XFS_MOUNT_COMPAT_IOSIZE

Replace XFS_MOUNT_COMPAT_IOSIZE with an inverted XFS_MOUNT_LARGEIO flag
that makes the usage more clear.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>