Currently we fail without printing any error message on "perf stat -e task-clock-msecs".

The reason is that the task-clock event is matched and the "-msecs" postfix is assumed
to be an event modifier - but is not recognized.

This patch changes the code to be more informative:

 $ perf stat -e task-clock-msecs true
 invalid event modifier: '-msecs'
 Run 'perf list' for a list of valid events and modifiers

And restructures the return value of parse_event_modifier() to allow
the printing of all variants of invalid event modifiers.
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-wlaw3dvz1ly6wple8l52cfca@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>