perf env: Cache the arch specific strerrno function in perf_env__arch_strerrno()

perf env: Cache the arch specific strerrno function in perf_env__arch_strerrno()

So that we don't have to go thru the series of strcmp(arch) calls for
each id -> string translation.

Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/20231201203046.486596-3-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>