add virtio-pci to defconfig

To use the emulated pci devices we need virtio-pci.

Signed-off-by: Stefan Zimmermann <stzi@linux.ibm.com>
diff --git a/arch/s390/configs/default_defconfig b/arch/s390/configs/default_defconfig
index 4f383b3..0578105 100644
--- a/arch/s390/configs/default_defconfig
+++ b/arch/s390/configs/default_defconfig
@@ -82,6 +82,7 @@
 CONFIG_PCI_DEBUG=y
 CONFIG_HOTPLUG_PCI=y
 CONFIG_HOTPLUG_PCI_S390=y
+CONFIG_VIRTIO_PCI=m
 CONFIG_CHSC_SCH=y
 CONFIG_CRASH_DUMP=y
 CONFIG_BINFMT_MISC=m