ftrace: Add self-tests for multiple function trace users

Add some basic sanity tests for multiple users of the function
tracer at startup.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_selftest_dynamic.c

@@ -5,3 +5,9 @@ int DYN_FTRACE_TEST_NAME(void)
 	/* used to call mcount */
 	return 0;
 }
+
+int DYN_FTRACE_TEST_NAME2(void)
+{
+	/* used to call mcount */
+	return 0;
+}