x86 mmiotrace: implement mmiotrace_printk()

Offer mmiotrace users a function to inject markers from inside the kernel.
This depends on the trace_vprintk() patch.

Signed-off-by: Pekka Paalanen <pq@iki.fi>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_mmiotrace.c

@@ -335,3 +335,8 @@ void mmio_trace_mapping(struct mmiotrace_map *map)
 	__trace_mmiotrace_map(tr, data, map);
 	preempt_enable();
 }
+
+int mmio_trace_printk(const char *fmt, va_list args)
+{
+	return trace_vprintk(0, fmt, args);
+}