No need to continually assign the control table addresses, provided we don't ever zero out the whole command header.
No need to continually assign the control table addresses, provided we don't
ever zero out the whole command header.

Also add some diagnostic checks to ensure we don't violate any of the
controller's DMA address/size restrictions.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars