ipmi(4): Add more watchdog error checks.

Add request submission status checks before checking req->ir_compcode,
otherwise it may be zero just because of initialization.

Add checks for req->ir_compcode errors in ipmi_reset_watchdog() and
ipmi_set_watchdog(). In first case explicitly check for 0x80, which
means timer was not previously set, that I found happening after BMC
cold reset. This change makes watchdog timer to recover instead of
permanently ignoring reset errors after BMC reset or upgraded.

MFC after: 2 weeks
Sponsored by: iXsystems, Inc.