perf record: Prepare picking perf_event_mmap_page from multiple evlists

perf record: Prepare picking perf_event_mmap_page from multiple evlists

Following commits introduce new evlists to record. This patch adjusts
record__pick_pc() and introduces perf_evlist__pick_pc() to read control
page from one specific evlist. record__pick_pc() will be improved to
search control page from multiple evlists.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1467023052-146749-4-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>