compositor-drm: Add missing drmModeFreeResources in drm_device_is_kms

Signed-off-by: Sergi Granell <xerpi.g.12@gmail.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
diff --git a/libweston/compositor-drm.c b/libweston/compositor-drm.c
index 4cb27b1..3f7e97e 100644
--- a/libweston/compositor-drm.c
+++ b/libweston/compositor-drm.c
@@ -3055,6 +3055,8 @@
 	b->drm.id = id;
 	b->drm.filename = strdup(filename);
 
+	drmModeFreeResources(res);
+
 	return true;
 
 out_res: