display: Fix dependency compile error

When enforce product I/F for Native modules, system_ext module
cannot link to product module and vice versa.
When PRODUCT_PRODUCT_VNDK_VERSION := current, all native modules
in product partition are in the product variant. Adding system_ext_specific
and vendor_available will create system_ext variant and vendor variant.

Change-Id: Id8953a6c65b346a4762c9d9d89f7c6c26d80fdfa

services/config/src/Android.bp

@@ -1,7 +1,7 @@
 cc_library_shared {
     name: "libdisplayconfig.qti",
     vendor_available: true,
-    product_specific: true,
+    system_ext_specific: true,
     cflags: [
         "-Wno-sign-conversion",
         "-Wno-unused-parameter",