Adding a new rule to the event grammar to be able to specify
values of additional attributes of symbolic event.

The new syntax for event symbolic definition is:

event_legacy_symbol:  PE_NAME_SYM '/' event_config '/' |
                      PE_NAME_SYM sep_slash_dc

event_config:         event_config ',' event_term | event_term

event_term:           PE_NAME '=' PE_NAME |
                      PE_NAME '=' PE_VALUE
                      PE_NAME

sep_slash_dc: '/' | ':' |

At the moment the config options are hardcoded to be used for legacy
symbol events to define several perf_event_attr fields. It is:

  'config'   to define perf_event_attr::config
  'config1'  to define perf_event_attr::config1
  'config2'  to define perf_event_attr::config2
  'period'   to define perf_event_attr::sample_period

Legacy events could be now specified as:
  cycles/period=100000/

If term is specified without the value assignment, then 1 is
assigned by default.
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-mgkavww9790jbt2jdkooyv4q@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>