perf evswitch: Introduce OPTS_EVSWITCH() for cmd line processing

All tools will want those, so provide a convenient way to get them.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: William Cohen <wcohen@redhat.com>
Link: https://lkml.kernel.org/n/tip-v16pe3sbf3wjmn152u18f649@git.kernel.org


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