FM: Make javaClassRef static to avoid SNS issues

Make javaClassRef static to avoid SNS issues since
it anyway has to get initialized once when classInitNative()
is being called.

Change-Id: If79089ff2c8a7c5663e7f5e5382705ed2feb35cd
diff --git a/jni/android_hardware_fm.cpp b/jni/android_hardware_fm.cpp
index 5cb7318..628559c 100644
--- a/jni/android_hardware_fm.cpp
+++ b/jni/android_hardware_fm.cpp
@@ -128,7 +128,7 @@
 static bool mCallbacksObjCreated = false;
 static jfieldID sCallbacksField;
 
-jclass javaClassRef;
+static jclass javaClassRef;
 static jmethodID method_psInfoCallback;
 static jmethodID method_rtCallback;
 static jmethodID method_ertCallback;