Allow vendor/cyngn overlays to override vendor/cm overlays

Change-Id: I4806f6ec8cd5b8171cbc4dac3cc1b93dbe941e92
(cherry picked from commit 5c5a2e8f08f92b2d75a50c4cfc2707ac076f357f)
diff --git a/config/common.mk b/config/common.mk
index 7b1b2bb..96f459f 100644
--- a/config/common.mk
+++ b/config/common.mk
@@ -324,4 +324,4 @@
 
 -include vendor/cyngn/product.mk
 
-$(call inherit-product-if-exists, vendor/extra/product.mk)
+$(call prepend-product-if-exists, vendor/extra/product.mk)