perf bpf: Add bpf__setup_output_event() strerror() counterpart

perf bpf: Add bpf__setup_output_event() strerror() counterpart

That is just bpf__strerror_setup_stdout() renamed to the more general
"setup_output_event" method, keep the existing stdout() as a wrapper.

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: https://lkml.kernel.org/n/tip-nwnveo428qn0b48axj50vkc7@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>