perf dso: Add missed dso__put to dso__load_kcore

perf dso: Add missed dso__put to dso__load_kcore

The kcore loading creates a set of list nodes that have reference
counted references to maps of the kcore. The list node freeing in the
success path wasn't releasing the maps, add the missing puts. It is
unclear why this leak was being missed by leak sanitizer.

Fixes: 83720209961f ("perf map: Move map list node into symbol")
Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250624190326.2038704-2-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>