perf tools: Leave DSO destruction to the map destruction

perf tools: Leave DSO destruction to the map destruction

As the way DSOs are created are normally via dsos__findnew, so that we
don't have to load the same dso multiple times for multiple maps (think
about /lib64/libc.so.6), so they may be shared and dso__delete() should
be left to be done as part of the map destruction process.

This will all be properly solved by reference counting struct dso, which
will be done soon.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-gbrohe1nvkjxw3u5a1bgj3yh@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>