No need for a private #define for the INQUIRY response_format value '2'. Just
use the new SID_SCSI2_RESPONSE.

VMD: vioscsi - add support for REPORT_LUNS opcode

ok mlarkin@

Add initial CD-ROM support to VMD via vioscsi.

* Adds 'cdrom' keyword to vm.conf(5) and '-r' to vmctl(8)
* Support various sized ISOs (Limitation of 4G ISOs on Linux guests)
* Known working guests: OpenBSD (primary), Alpine Linux (primary),
CentOS 6 (secondary), Ubuntu 17.10 (secondary).
NOTE: Secondary indicates some issue(s) preventing full/reliable
functionality outside the scope of the vioscsi work.
* If the attached disks are non-bootable (i.e. empty), SeaBIOS (vmd's
default BIOS) will boot from CD-ROM.

ok mlarkin@, jca@