tests/util: Add vkms driver

Add an entry for the "vkms" driver, so that the test utilities work with
the vkms driver without passing the -M argument.

Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Yi Xie <yixie@google.com>

tests/util/kms.c

@@ -125,6 +125,7 @@ static const char * const modules[] = {
 	"mxsfb-drm",
 	"simpledrm",
 	"imx-lcdif",
+	"vkms",
 };
 
 int util_open(const char *device, const char *module)