It's confusing which one is effective when the both options are given.
The current code happens to use -c in this case but users might not be
aware of it.  We can change it to complain about that instead of relying
on the implicit priority.

Before:

  $ perf record -c 111111 -F 99 true
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.031 MB perf.data (8 samples) ]

  $ perf evlist -F
  cycles: sample_period=111111
  $

After:
  $ perf record -c 111111 -F 99 true
  cannot set frequency and period at the same time
  $

So this change can break existing usages, but I think it's rare to have
both options and it'd be better changing them.
Suggested-by: Alexey Alexandrov <aalexand@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210402094020.28164-1-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>