bpf, doc: update list of architectures that do eBPF JIT

update the list and remove 'in the future' statement,
since all still alive 64-bit architectures now do eBPF JIT.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>