bhyve command-line option order

I wrote a change to vm-bhyve[1] to be able to pass the options to bhyve 
in the correct order to use GPU passthru.  In the incorrect order, bhyve 
will return an error.  The question was raised:  Is it expected that 
bhyve will return an error depending upon the order of command-line 
arguments, or should it be handling this scenario?

The issue is when "-s 31, lpc" is presented to bhyve.  If it is passed 
prior to "-o pci.0.31.0.pcireg.vendor=host", then there is no error. 
However, if it is in the opposite order, this is returned:

$ bhyve ... -o pci.0.31.0.pcireg.vendor=host -s 31,lpc ...
pci slot 0:31:0 already occupied!

I will be updating my PR to make things a bit easier regardless of the 
answer, but it would be nice to know if this is intended or not.

Thank you.

Sean
   1. https://github.com/freebsd/vm-bhyve/pull/56
-- 
scf@FreeBSD.org