linux-initrd: Add the 'virtio_console' module for QEMU guests.

* gnu/system/linux-initrd.scm (base-initrd)[virtio-modules]: Add
  "virtio_console".

gnu/system/linux-initrd.scm

@@ -166,7 +166,8 @@ (define* (base-initrd file-systems
 loaded at boot time in the order in which they appear."
   (define virtio-modules
     ;; Modules for Linux para-virtualized devices, for use in QEMU guests.
-    '("virtio_pci" "virtio_balloon" "virtio_blk" "virtio_net"))
+    '("virtio_pci" "virtio_balloon" "virtio_blk" "virtio_net"
+      "virtio_console"))
 
   (define cifs-modules
     ;; Modules needed to mount CIFS file systems.