perf tests: Add missing pthread.h include for CPU_*() macros

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-dfcynqzvecsu55zmpxub9jgv@git.kernel.org


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