i2c: New co-maintainer

Ben Dooks agreed to become my co-maintainer for the i2c subsystem. In
particular, Ben will help with drivers for embedded systems, of which
my experience is inexistent. Thanks Ben and welcome on board!

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Ben Dooks <ben-linux@fluff.org>