test: dm: virtio_rng: Test virtio-rng with faked device

Add a regression test for virtio-rng reading beyond the end of its
buffer if the virtio device provides an invalid length.

Signed-off-by: Andrew Scull <ascull@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/Makefile b/test/dm/Makefile
index 809f0f2..caea52f 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -110,6 +110,7 @@
 ifeq ($(CONFIG_VIRTIO_SANDBOX),y)
 obj-y += virtio.o
 obj-$(CONFIG_VIRTIO_RNG) += virtio_device.o
+obj-$(CONFIG_VIRTIO_RNG) += virtio_rng.o
 endif
 ifeq ($(CONFIG_WDT_GPIO)$(CONFIG_WDT_SANDBOX),yy)
 obj-y += wdt.o