Enable the hardclock-based watchdog previously considional on the SW_WATCHDOG
option whenever hardware watchdogs are not found, and watchdogd attempts to
enable the watchdog. The SW_WATCHDOG option still causes the sofware
watchdog to be enabled even if there is a hardware watchdog. This does
not change the other software-based watchdog enabled by the --softtimeout
option to watchdogd.
Note that the code to reprime the watchdog during kernel core dumps is
no longer conditional on SW_WATCHDOG. I think this was previously a bug.