perf evsel: Introduce evsel__name_is() method to check if the evsel name is equal...

perf evsel: Introduce evsel__name_is() method to check if the evsel name is equal to a given string

This makes the logic a bit clear by avoiding the !strcmp() pattern and
also a way to intercept the pointer if we need to do extra validation on
it or to do lazy setting of evsel->name via evsel__name(evsel).

Reviewed-by: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/ZEGLM8VehJbS0gP2@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>