perf symbols: Do not open device files

The dso__read_binary_type_filename gets the dso's file name to open. We
need to check it for regular file before trying to open it, otherwise we
might get stuck with device file.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20160920161245.GA8995@krava


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