xfs: remove the mappedbno argument to xfs_da_get_buf

Use the xfs_da_get_buf_daddr function directly for the two callers
that pass a mapped disk address, and then remove the mappedbno argument.

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