xfs: reflink should force the log out if mounted with wsync

Reflink should force the log out to disk if the filesystem was mounted
with wsync, the same as most other operations in xfs.

[Note: XFS_MOUNT_WSYNC is set when the admin mounts the filesystem
with either the 'wsync' or 'sync' mount options, which effectively means
that we're classifying reflink/dedupe as IO operations and making them
synchronous when required.]

Fixes: 3fc9f5e4 ("xfs: remove xfs_reflink_remap_range")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
[darrick: add more to the changelog]
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>