perf stat: Add output file argument to print_shadow_stats function

perf stat: Add output file argument to print_shadow_stats function

As preparation for moving shadow counters code into its own object.

Signed-off-by: Jiri Olsa <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>