xfs: remove the mappedbno argument to xfs_da_read_buf

xfs: remove the mappedbno argument to xfs_da_read_buf

Source kernel commit: cd2c9f1b544b8f5e1ca1874032fd669d74946a6d

Move the code for reading an already mapped block into
xfs_da3_node_read_mapped, which is the only caller ever passing a block
number in the mappedbno argument and replace the mappedbno argument with
the simple xfs_dabuf_get flags.

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>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>