It is valid for a watchdog driver to have 0 for a "min" and "max"
timeout if the driver doesn't need the core to enforce the concepts of
min and max. The s3c2410_wdt driver is one such driver. Specifically
it can be hard for that driver to come up with a static "max" on all
platforms without a lot more information since the input clock on
S3C2410 and S3C2440 can change with DVFS.
As written, watchdog_init_timeout() will not ever read "timeout-sec"
on these drivers since watchdog_timeout_invalid() will _never_ return
true. Change to not consider a timeout_parm of 0 as valid even if
min/max aren't specified by the driver. Also handle the case when
there is no min/max and no "timeout-sec" property.
Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>