perf dso: Declare dso const as needed

Declare dso const, so that functions can be called with const struct *dso.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20230424055107.12105-2-adrian.hunter@intel.com


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