Clean up internal usage of g*Converter for manifest/matrix.

Change to toXml / fromXml instead.

Test: pass
Change-Id: I9326c6ea5003800108f4f9d6ac831ba815c21f0b
diff --git a/VintfObject.cpp b/VintfObject.cpp
index 2ef4e79..0a2b49c 100644
--- a/VintfObject.cpp
+++ b/VintfObject.cpp
@@ -469,7 +469,7 @@
     if (status != OK) {
         return status;
     }
-    if (!gCompatibilityMatrixConverter(out, content, error)) {
+    if (!fromXml(out, content, error)) {
         if (error) {
             error->insert(0, "Cannot parse " + path + ": ");
         }