perf bpf: Make bpf__for_each_stdout_map() generic

perf bpf: Make bpf__for_each_stdout_map() generic

By passing a 'name' arg, that will eventually be used to setup more
"bpf-output" events, e.g. to create a event where to create raw_syscalls
like events that in addition to the syscall arguments will also copy the
pointer contents being passed from/to userspace.

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-talrnxps9p3qozk3aeh91fgv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>