xfs: move transaction handling to xfs_bmapi_convert_delalloc

xfs: move transaction handling to xfs_bmapi_convert_delalloc

Source kernel commit: 491ce61e939f76399e344b0414dc5a4c08c1f0cf

No need to deal with the transaction and the inode locking in the
caller. Note that we also switch to passing whichfork as the second
paramter, matching what most related functions do.

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>