perf tools: Do not provide dup sched_getcpu() prototype on Android

The Bionic libc has this definition, so don't duplicate it.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Chris Phlipot <cphlipot0@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-rmd19832zkt07e4crdzyen9z@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>