watchdog: retry with larger timeout value if effective timeout is 0

watchdog: retry with larger timeout value if effective timeout is 0

Some watchdog drivers, such as w83793, have a very low timeout granularity
of only one minute. The procd default timeout of 30s will yield an effective
timeout of 0 with this driver, leading to an almost instant reset once
activated.

In order to gracefully deal with watchdogs having no sub-30s resolution,
check that the effectively calculated timeout returned by the ioctl() call
is zero and retry with a duplicated timeout value in this case.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>