Use cirrus driver for QEMU

Moving to the cirrus driver (instead of std) so we can support
cirrus-fb, in preparation for nonroot-X support.

BUG=chromium-os:388
TEST=local build, run with x86-generic

Change-Id: Ic7d5776f673ac3c15680d62331345d55985f1d73
Reviewed-on: https://gerrit.chromium.org/gerrit/39900
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Tested-by: John Sheu <sheu@chromium.org>
Commit-Queue: John Sheu <sheu@chromium.org>

image_to_vm.sh

@@ -241,7 +241,7 @@ fi
 
 if [ "${FLAGS_format}" == "qemu" ]; then
   echo "If you have qemu-kvm installed, you can start the image by:"
-  echo "sudo kvm -m ${FLAGS_mem} -vga std -pidfile /tmp/kvm.pid -net nic,model=virtio " \
-       "-net user,hostfwd=tcp::9222-:22 \\"
-  echo "        -hda ${FLAGS_to}/${DEFAULT_QEMU_IMAGE}"
+  echo "sudo kvm -m ${FLAGS_mem} -vga cirrus -pidfile /tmp/kvm.pid" \
+       "-net nic,model=virtio -net user,hostfwd=tcp::9222-:22 \\"
+  echo "-hda ${FLAGS_to}/${DEFAULT_QEMU_IMAGE}"
 fi

lib/cros_vm_lib.sh

@@ -97,7 +97,7 @@ start_kvm() {
 
     sudo "${KVM_BINARY}" -m 2G \
       -smp 4 \
-      -vga std \
+      -vga cirrus \
       -pidfile "${KVM_PID_FILE}" \
       -daemonize \
       ${net_option} \