perf tools: Fix lockup using 32-bit compat vdso

The __machine__findnew_compat() function is called only from
__machine__findnew_vdso_compat() which is called only from
machine__findnew_vdso() which already holds machine->dsos.lock, so
remove locking from __machine__findnew_compat().

This manifests itself tracing 32-bit programs with a 64-bit perf.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1436267618-20521-1-git-send-email-adrian.hunter@intel.com


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