Add Wake-on-LAN control via dev.asmc.0.wol sysctl.
Apple Mac Minis support Wake-on-LAN from powered-off state (S5/G2)
via the AUPO (Auto Power On) SMC key. Setting AUPO=0x01 before
shutdown enables the system to wake via magic packet.
This change adds a convenience sysctl:
dev.asmc.0.wol (read/write, 0=disabled, 1=enabled)
The AUPO key is volatile and resets to 0x00 on boot, so it must
be set before each shutdown to enable WoL from powered-off state.
Tested on: Mac Mini 5,1 (FreeBSD 16.0-CURRENT)