tracing/fastboot: include missing headers

For now include/trace/boot.h doesn't need to include necessary headers
for its functions and structures because the files that include it already
do it.

But boot.h could be needed as well for further uses on other files.
So, this patch adds the necessary headers for future purposes...
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/trace/boot.h

 #ifndef _LINUX_TRACE_BOOT_H
 #define _LINUX_TRACE_BOOT_H
 
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+#include <linux/init.h>
+
 /*
  * Structure which defines the trace of an initcall
  * while it is called.