perf stat: Fix printout vertical alignment

Before:

 |
 | Performance counter stats for '/home/mingo/hackbench 20' (5 runs):
 |
 |        71,321,607 instructions:u           #    0.42  insns per cycle  ( +-  0.00% )
 |       168,040,009 cycles:u                 #    0.000 GHz                      ( +-  0.81% )
 |
 |        1.468002368  seconds time elapsed  ( +-  1.33% )
 |

After:

 |
 | Performance counter stats for '/home/mingo/hackbench 20' (5 runs):
 |
 |        71,321,607 instructions:u           #    0.42  insns per cycle          ( +-  0.00% )
 |       168,040,009 cycles:u                 #    0.000 GHz                      ( +-  0.81% )
 |
 |        1.468002368  seconds time elapsed  ( +-  1.33% )
 |

The last column (stddev noise) is properly aligned, vertically.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-7y40wib8n1eqio7hjpn0dsrm@git.kernel.org


Signed-off-by: Ingo Molnar <mingo@elte.hu>