I basically combined Paul's patches with additions that I had made
for PCI scatter gather.
I also tried more carefully to avoid problems with the same token
assigned multiple times while trying to use the base address in the
token if possible to gain as much backward compatibility as possible
for broken DRI clients.

From: Paul Mackerras <paulus@samba.org> and Egbert Eich <eich@suse.de>
Signed-off-by: Dave Airlie <airlied@linux.ie>