To go from strarrays strings to its indexes.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-wta0qvo207z27huib2c4ijxq@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>