tracing: Fix build breakage without CONFIG_PERF_EVENTS (again)

Today's -next fails to link for me:

kernel/built-in.o:(.data+0x178e50): undefined reference to `perf_ftrace_event_register'

It looks like multiple fixes have been merged for the issue fixed by
commit fa73dc94 (tracing: Fix build breakage without CONFIG_PERF_EVENTS)
though I can't identify the other changes that have gone in at the
minute, it's possible that the changes which caused the breakage fixed
by the previous commit got dropped but the fix made it in.

Link: http://lkml.kernel.org/r/1334307179-21255-1-git-send-email-broonie@opensource.wolfsonmicro.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.h

@@ -836,11 +836,11 @@ extern const char *__stop___trace_bprintk_fmt[];
 		     filter)
 #include "trace_entries.h"
 
-#ifdef CONFIG_FUNCTION_TRACER
+#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_FUNCTION_TRACER)
 int perf_ftrace_event_register(struct ftrace_event_call *call,
 			       enum trace_reg type, void *data);
 #else
 #define perf_ftrace_event_register NULL
-#endif /* CONFIG_FUNCTION_TRACER */
+#endif
 
 #endif /* _LINUX_KERNEL_TRACE_H */