perf maps: Set the kmaps for newly created/added kernel maps

When using __maps__insert_sorted() the map kmaps field needs to be
initialized, as we need kernel maps to work with map__kmap().

Fix it by using the newly introduced map__set_kmap() method.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/lkml/Z74V0hZXrTLM6VIJ@x1
Link: https://lore.kernel.org/r/20250228211734.33781-3-acme@kernel.org


Signed-off-by: Namhyung Kim <namhyung@kernel.org>