perf evsel: Fix period/freq terms setup

Stephane reported that we don't set properly PERIOD sample type for
events with period term defined.

Before:
  $ perf record -e cpu/cpu-cycles,period=1000/u ls
  $ perf evlist -v
  cpu/cpu-cycles,period=1000/u: ... sample_type: IP|TID|TIME|PERIOD, ...

After:
  $ perf record -e cpu/cpu-cycles,period=1000/u ls
  $ perf evlist -v
  cpu/cpu-cycles,period=1000/u: ... sample_type: IP|TID|TIME, ...

Setting PERIOD sample type based on period term setup.

Committer note:

When we use -c or a period=N term in the event definition, then we don't
need to ask the kernel, for this event, via perf_event_attr.sample_type
|= PERF_SAMPLE_PERIOD, to put the event period in each sample for this
event, as we know it already, it is in perf_event_attr.sample_period.

Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Stephane Eranian <eranian@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180201083812.11359-2-jolsa@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>