bpf: handle jset (if a & b ...) as a jump in CFG computation

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

bpf: handle jset (if a & b ...) as a jump in CFG computation

BPF_JSET is a conditional jump and currently verifier.c:can_jump() does not know about that. This can lead to incorrect live registers and SCC computation.

E.g. in the following example:

1: r0 = 1; 2: r2 = 2; 3: if r1 & 0x7 goto +1; 4: exit; 5: r0 = r2; 6: exit;

W/o this fix insn_successors(3) will return only (4), a jump to (5) would be missed and r2 won't be marked as alive at (3).