xen: expose support for poweroff/reboot/suspend on xenbus

[royger]

Summary

Some toolstacks won't attempt the signal power actions on xenbus unless the VM
explicitly exposes support for them. FreeBSD supports all power actions, hence
signal on xenbus such support by setting the nodes to the value of "1".

Sponsored by: Cloud Software Group

[markj]

This looks ok to me aside from style nits. I don't know Xen well enough to properly review the substance of the change.

sys/dev/xen/control/control.c

401

Extra newline.

502

Extra newline.

508

Extra newline.

[royger]

Thanks for the review, will get the extra newlines removed and this committed.

sys/dev/xen/control/control.c

401

Oh, we finally changed the style to not mandate an empty newline if there are no local varaibles in a function:

static void
usage(void)
{
       /* Optional blank line goes here. */

Optionally, insert a blank line at the beginning of functions with no
local variables.   Older versions of this style document required the
blank line convention, so it is widely used in existing code.