xfs: move pre/post-bmap tracing into xfs_iext_update_extent

xfs_iext_update_extent already has basically all the information needed
to centralize the bmap pre/post tracing.  We just need to pass inode +
bmap state instead of the inode fork pointer to get all trace annotations.

In addition to covering all the existing trace points this gives us
tracing coverage for the extent shifting operations for free.

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>