Add DT entries for main domain watchdog0 and 1 instances on the J721e well as RTI1-based watchdog on the AM65x. RTI0 does not work for this purpose on the AM65x, so leave it out. On AM65x, we mark the power-domain as shared because RTI firmware such as https://github.com/siemens/k3-rti-wdt may request it as well in order to prevent accidental shutdown of the watchdog. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>