qemu: dont set mq=on,vectors=N for virtio-net-device

Setting vcpu > 1 for qemu guests would result in the following error
during guest startup:

  qemu-system-x86_64: -device virtio-net-device,netdev=host1, \
    mac=02:00:00:00:00:01,mq=on,vectors=6: Property \
    'virtio-net-device.vectors' not found

lib/runners/qemu.nix

@@ -250,7 +250,7 @@ in {
             (microvmConfig.cpu == null && system != "x86_64-linux")
           ) ",romfile="
         }${
-          lib.optionalString tapMultiQueue ",mq=on,vectors=${toString (2 * vcpu + 2)}"
+          lib.optionalString (tapMultiQueue && requirePci) ",mq=on,vectors=${toString (2 * vcpu + 2)}"
         }"
       ]) interfaces
     )