perf trace beauty eventfd: No need to include eventfd.h

perf trace beauty eventfd: No need to include eventfd.h

Old systems such as RHEL5 lack this file, and what we need is
already under ifdefs, so just ditch this #include.

Cc: Adrian Hunter <adrian.hunter@intel.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-dzbjfllw6znuoy37skwnwa4r@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>