i2c-algo-pcf: Multi-master lost-arbitration improvement

Improve lost-arbitration handling of PCF8584.  This is necessary for
support of a currently out-of-kernel driver for Sun Microsystems E250
environmental management; perhaps others.

Signed-off-by: Eric Brower <ebrower@gmail.com>
Acked-by: Dan Smolik <marvin@mydatex.cz>
Signed-off-by: Jean Delvare <khali@linux-fr.org>