powerd enabled on RPI 15-current snapshots

powerd is now enabled by default on the 15-current RPI snapshot for this week,
FreeBSD-15.0-CURRENT-arm64-aarch64-RPI-20240111-a61d2c7fbd3c-267507.img.xz.
I encourage people to try it, and/or try enabling powerd on existing systems
if it isn't yet (unless running full speed all the time, which is not the
default).  The change is simply to add

	powerd_enable="YES"

to /etc/rc.conf, then run "service powerd start".  The addition can be done with
"sysrc powerd_enable=YES".

I'm interested to hear about any problems in particular.  I will add a RELNOTES
entry about this, and any recommendations are welcomed.  I plan to MFC this in
about a month if experience is generally good.

		Mike