perf tests vmlinux-kallsyms: Use map__for_each_symbol() instead of open coded equivalent

perf tests vmlinux-kallsyms: Use map__for_each_symbol() instead of open coded equivalent

We had this much shorter map__for_each_symbol() helper for ages, use it
and kill one more map_type use outside the code, in the tools.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-iswqjy1elghc5jjvr0nds3nc@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>