xfs: remove inst_t

We can simply use a void pointer to pass a long return addresses in the
debugging helpers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --cc fs/xfs/xfs_error.c
Simple merge

diff --cc fs/xfs/xfs_error.h
Simple merge

diff --cc fs/xfs/xfs_linux.h
Simple merge