modetest: close the device on exit

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Tested-by: Ezequiel Garcia <ezequiel@collabora.com>

tests/modetest/modetest.c

@@ -2150,6 +2150,7 @@ int main(int argc, char **argv)
 	}
 
 	free_resources(dev.resources);
+	drmClose(dev.fd);
 
 	return 0;
 }