bpf, doc: fix typo on bpf_asm descriptions

Fix description of some of the bpf_asm tool related jump instructions
and generally move them to format A <op> k.

Reported-by: Sebastian Amend <sebastian.amend@googlemail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>