xfs: pass state not whichfork to trace_xfs_extlist

When xfs_bmap_trace_exlist called trace_xfs_extlist,
it sent in the "whichfork" var instead of the bmap "state"
as expected (even though state was already set up for this
purpose).

As a result, the xfs_bmap_class in tracing code used
"whichfork" not state in xfs_iext_state_to_fork(), and got
the wrong ifork pointer.  It all goes downhill from
there, including an ASSERT when ifp_bytes is empty
by the time it reaches xfs_iext_get_ext():

XFS: Assertion failed: idx < ifp->if_bytes / sizeof(xfs_bmbt_rec_t)
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -531,7 +531,7 @@ xfs_bmap_trace_exlist(
 	ifp = XFS_IFORK_PTR(ip, whichfork);
 	ASSERT(cnt == xfs_iext_count(ifp));
 	for (idx = 0; idx < cnt; idx++)
-		trace_xfs_extlist(ip, idx, whichfork, caller_ip);
+		trace_xfs_extlist(ip, idx, state, caller_ip);
 }
 
 /*