tracing: function graph tracer, fix

fix return-tracer => graph-tracer namespace rename fallout.
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/entry_32.S

@@ -1189,7 +1189,7 @@ ENTRY(mcount)
 	cmpl $ftrace_stub, ftrace_trace_function
 	jnz trace
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-	cmpl $ftrace_stub, ftrace_graph_function
+	cmpl $ftrace_stub, ftrace_graph_return
 	jnz ftrace_graph_caller
 #endif
 .globl ftrace_stub