scsi: device version property

scsi: device version property

This patch adds a new property named 'ver' to scsi-disk which allows to
specify the version which the virtual disk/cdrom should report to the
guest.  By default this is the qemu version (i.e. 0.12).  usage:

  -drive if=none,id=disk,file=...
  -device lsi
  -device scsi-disk,drive=disk,bus=scsi.0,unit=0,ver=42

You can also switch the version for all scsi drives using:

  -global scsi-disk.ver=42

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>