bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR

maybe_fork_scalars() is called for both BPF_AND and BPF_OR when the

source operand is a constant. When dst has signed range [-1, 0], it

forks the verifier state: the pushed path gets dst = 0, the current

path gets dst = -1.

For BPF_AND this is correct: 0 & K == 0.

For BPF_OR this is wrong: 0 | K == K, not 0.

The pushed path therefore tracks dst as 0 when the runtime value is K,

producing an exploitable verifier/runtime divergence that allows

out-of-bounds map access.

Fix this by passing env->insn_idx (instead of env->insn_idx + 1) to

push_stack(), so the pushed path re-executes the ALU instruction with

dst = 0 and naturally computes the correct result for any opcode.