nfp: bpf: complete ALU32 logic shift supports

The following ALU32 logic shift supports are missing:

  BPF_ALU | BPF_LSH | BPF_X
  BPF_ALU | BPF_RSH | BPF_X
  BPF_ALU | BPF_RSH | BPF_K

For BPF_RSH | BPF_K, it could be implemented using NFP direct shift
instruction. For the other BPF_X shifts, NFP indirect shifts sequences need
to be used.

Separate code-gen hook is assigned to each instruction to make the
implementation clear.

Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>