perf tools: Drop strxfrchar(), use strreplace() equivalent from kernel

No change in behaviour intended, just reducing the codebase and using
something available in tools/lib/.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-oyi6zif3810nwi4uu85odnhv@git.kernel.org


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