drivers/watchdog: Check Return Value

commit  467435a4531e57d814feaff71272ae818c6db564 from
https://github.com/axxia/linux-yocto.git axxia-linux/v5.10/standard/axxia-dev/base

In sp804_wdt_axxia.c, check that rate is not zero before
using it as a divisor.

Signed-off-by: John Jacques <john.jacques@intel.com>
Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>