perf callchain: Use debug_frame if eh_frame is unusable

When NO_LIBUNWIND_DEBUG_FRAME=0, use the .debug_frame if the .eh_frame
doesn't contain the approprate unwind tables.

Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rabin Vincent <rabinv@axis.com>
Link: http://lkml.kernel.org/r/1443379079-29133-3-git-send-email-rabin.vincent@axis.com


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