add virtio-scsi driver

virtio-scsi is a simple HBA that talks to the host via a single
vring.  The implementation looks like a hybrid of usb-msc and
virtio-blk.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/src/boot.c b/src/boot.c
index e26dad1..c737ba4 100644
--- a/src/boot.c
+++ b/src/boot.c
@@ -128,6 +128,20 @@
     return find_prio(desc);
 }
 
+int bootprio_find_scsi_device(struct pci_device *pci, int target, int lun)
+{
+    if (!CONFIG_BOOTORDER)
+        return -1;
+    if (!pci)
+        // support only pci machine for now
+        return -1;
+    // Find scsi drive - for example: /pci@i0cf8/scsi@5/channel@0/disk@1,0
+    char desc[256], *p;
+    p = build_pci_path(desc, sizeof(desc), "*", pci);
+    snprintf(p, desc+sizeof(desc)-p, "/*@0/*@%d,%d", target, lun);
+    return find_prio(desc);
+}
+
 int bootprio_find_ata_device(struct pci_device *pci, int chanid, int slave)
 {
     if (!CONFIG_BOOTORDER)