A syscon_power instance can handle either poweroff or reboot, but not
both. If the instance handles reboot then set its priority to be after
shutdown_panic.
This is to provide uniform experience with other platforms.
(cherry picked from commit 5f7312a0d70c607afa9ce24ccd757321d043e02c)
The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.
Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix