trace: Use fprintf_function (format checking)

fprintf_function adds format checking with GCC_FMT_ATTR.

Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: NStefan Weil <weil@mail.berlios.de>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

simpletrace.h

@@ -29,10 +29,10 @@ void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3);
 void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4);
 void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5);
 void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6);
-void st_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...));
-void st_print_trace_events(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...));
+void st_print_trace(FILE *stream, fprintf_function stream_printf);
+void st_print_trace_events(FILE *stream, fprintf_function stream_printf);
 bool st_change_trace_event_state(const char *tname, bool tstate);
-void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...));
+void st_print_trace_file_status(FILE *stream, fprintf_function stream_printf);
 void st_set_trace_file_enabled(bool enable);
 bool st_set_trace_file(const char *file);
 void st_flush_trace_buffer(void);