perf_counter tools: kerneltop: display per function percentage along with event count

perf_counter tools: kerneltop: display per function percentage along with event count

------------------------------------------------------------------------------
 KernelTop:   90551 irqs/sec  kernel:15.0% [NMI, 100000 CPU cycles],  (all, 4 CPUs)
------------------------------------------------------------------------------

             events    pcnt         RIP          kernel function
  ______     ______   _____   ________________   _______________

           16871.00 - 19.1% - ffffffff80328e20 : clear_page_c
            8810.00 -  9.9% - ffffffff8048ce80 : page_fault
            4746.00 -  5.4% - ffffffff8048cae2 : _spin_lock
            4428.00 -  5.0% - ffffffff80328e70 : copy_page_c
            3340.00 -  3.8% - ffffffff80329090 : copy_user_generic_string!
            2679.00 -  3.0% - ffffffff8028a16b : get_page_from_freelist
            2254.00 -  2.5% - ffffffff80296f19 : unmap_vmas
            2082.00 -  2.4% - ffffffff80297e19 : handle_mm_fault
            1754.00 -  2.0% - ffffffff80288dc8 : __rmqueue_smallest
            1553.00 -  1.8% - ffffffff8048ca58 : _spin_lock_irqsave
            1400.00 -  1.6% - ffffffff8028cdc8 : release_pages
            1337.00 -  1.5% - ffffffff80285400 : find_get_page
            1335.00 -  1.5% - ffffffff80225a23 : do_page_fault
            1299.00 -  1.5% - ffffffff802ba8e7 : __d_lookup
            1174.00 -  1.3% - ffffffff802b38f3 : __link_path_walk
            1155.00 -  1.3% - ffffffff802843e1 : perf_swcounter_ctx_event!
            1137.00 -  1.3% - ffffffff8028d118 : ____pagevec_lru_add
             963.00 -  1.1% - ffffffff802a670b : kmem_cache_alloc
             885.00 -  1.0% - ffffffff8024bc61 : __wake_up_bit

Display per function percentage along with event count.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>