watchdog: hpwdt: Adjust documentation to match latest kernel module parameters.

Adjust documentation to match latest kernel module parameters.

Signed-off-by: Nigel Croxon <nigel.croxon@hpe.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>