tracing/fastboot: add better resolution to initcall debug/tracing

Change the time resolution for initcall_debug to microseconds, from
milliseconds.  This is handy to determine which initcalls you want to work
on for faster booting.

One one of my test machines, over 90% of the initcalls are less than a
millisecond and (without this patch) these are all reported as 0 msecs.
Working on the 900 us ones is more important than the 4 us ones.

With 'quiet' on the kernel command line, this adds no significant overhead
to kernel boot time.

Signed-off-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 5812dba..a3d4615 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -215,9 +215,9 @@
 
 struct boot_trace {
 	pid_t			caller;
-	char 			func[KSYM_NAME_LEN];
+	char			func[KSYM_NAME_LEN];
 	int			result;
-	unsigned long long	duration;
+	unsigned long long	duration;		/* usecs */
 	ktime_t			calltime;
 	ktime_t			rettime;
 };