bpf, x32: Fix bug with ALU64 {LSH, RSH, ARSH} BPF_K shift by 0

commit 6fa632e719eec4d1b1ebf3ddc0b2d667997b057b upstream.

The fix only affects x32 bpf jit, and it is critical to use x32 bpf jit on a unpatched system, so I think we should backport it to the only affected stable kernel version: v4.19

Thanks.