to the qemu one, and uses the same i/o ports but with different
messaging. Requires the 'bootrom' option to be enabled.
This is used by UEFI (and potentially other BIOSs/firmware) to
request information from bhyve. Currently, only the number of
vCPUs is made available, with more to follow.
A very large thankyou to Ben Perrault who helped out testing
an earlier version of this, and bhyve/Windows in general.
Reviewed by: tychon
Discussed with: neel
Sponsored by: Nahanni Systems
