perf tools: Fix dso_id inode generation comparison

Synthesized MMAP events have zero ino_generation, so do not compare
them to DSOs with a real ino_generation otherwise we end up with a DSO
without a build id.

Fixes: 0e3149f8 ("perf dso: Move dso_id from 'struct map' to 'struct dso'")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: kvm@vger.kernel.org
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220711093218.10967-2-adrian.hunter@intel.com


[ Added clarification to the comment from Ian + more detailed explanation from Adrian ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>