ppc: bpf: implement jitting of BPF_ALU | BPF_ARSH | BPF_*

This patch implements code-gen for BPF_ALU | BPF_ARSH | BPF_*.

Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>