perf map: Use map->dso->kernel + map__kmaps() in map__kmaps()

Its equivalent to using map->groups to obtain the machine struct.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-bdbazuj4ggrmzxdviaqdrdwh@git.kernel.org


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