perf tools: Improve robustness of topology parsing code

This patch improves the robustness of the build_cpu_topo() routine by
allowing either the CPU parsing or the thread parsing to fail and yet
get perf to produce some topology data which could be useful for the
analysis.

Without this patch, if the cpu parsing fails, the thread parsing is not
attempted vice-versa.

Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130814100426.GA3444@quad


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