lockstat: Report avg wait and hold times

While both the nr and total times are showed, having the avg
lock hold and wait times show in the report is quite useful when
working on performance related issues. Furthermore, I find
myself constantly doing the calculations manually.

In addition, some of the documentation examples were changed to
easily update them to show the two new columns. No textual
change otherwise, as descriptions match the lockstat output.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: aswin@hp.com
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1380746928.2313.14.camel@buesod1.americas.hpqcorp.net
[ Fixlets: changed a seq_printf() to seq_puts(), converted spaces to tabs. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>