Error message should use stderr for verbose (-v), otherwise
message will be lost for:

 $ ./perf stat -v <cmd>  > /dev/null

For example on AMD bus-cycles event is not available so now
it looks like:

 $ ./perf stat -v -e bus-cycles ls > /dev/null
Error: counter 0, sys_perf_counter_open() syscall returned with -1 (Invalid argument)

 Performance counter stats for 'ls':

  <not counted>  bus-cycles

    0.006765877  seconds time elapsed.
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1245757369.3776.1.camel@localhost.localdomain>
Signed-off-by: NIngo Molnar <mingo@elte.hu>