perf kvm stat live: Use perf_evlist__add_pollfd() instead of local equivalent

perf kvm stat live: Use perf_evlist__add_pollfd() instead of local equivalent

Since we can add file descriptors to the evlist pollfd and it will
autogrow, no need to copy all events to a local pollfd array, just add
the timer and stdin file descriptors.

Reviewed-by: David Ahern <dsahern@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-2hvp9iromiheh6rl4oaa08x5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>