perf bench: Move HAVE_PTHREAD_ATTR_SETAFFINITY_NP into bench.h

Both futex and epoll need this call, and can cause build failure on
systems that don't have it pthread_attr_setaffinity_np().

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Link: http://lkml.kernel.org/r/20181109210719.pr7ohayuwqmfp2wl@linux-r8p5
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>