Add a simple fiemap implementation based on iomap_ops, partially based
on a previous implementation from Bob Peterson <rpeterso@redhat.com>.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>