When configuring event perf checked a wrong condition that user
specified both of freq (-F) and period (-c) or the event has no
default value.  This worked because most of events don't have default
value and only tracepoint events have default of 1 (and it's not
desirable to change it for those events).

However, Andi's downloadable event patch changes the situation so it
cannot change the value for those events.  Fix it by allowing override
the default value if user gives one of the options.

  $ perf record -a -e uops_retired.all -F 4000 sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.325 MB perf.data (~14185 samples) ]

  $ perf evlist -F
  cpu/uops_retired.all/: sample_freq=4000
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1402292617-26278-1-git-send-email-namhyung@kernel.orgSigned-off-by: Jiri Olsa <jolsa@kernel.org>