xfs: change the xfs_iext_insert / xfs_iext_remove

Change the xfs_iext_insert / xfs_iext_remove prototypes to pass more
information which will allow pushing the trace points from the callers
into those functions.  This includes folding the whichfork information
into the state variable to minimize the addition stack footprint.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>