Get rid of call enum.

Bug: 31758541
Test: hidl_test, hardware/interfaces mma, manual inspection of output
files

Change-Id: I16c076dbff9b0b8688e2492b0b9c97e9f6d48943
diff --git a/Method.cpp b/Method.cpp
index 7d7717a..95a688a 100644
--- a/Method.cpp
+++ b/Method.cpp
@@ -52,6 +52,14 @@
     return *mAnnotations;
 }
 
+void Method::setSerialId(size_t serial) {
+    mSerial = serial;
+}
+
+size_t Method::getSerialId() const {
+    return mSerial;
+}
+
 void Method::generateCppSignature(Formatter &out,
                                   const std::string &className,
                                   bool specifyNamespaces) const {