bpf_dbg: fix wrong register usage

The AND instruction is erroneously using the X register instead
of the K register.
Signed-off-by: NBrendan Hickey <bhickey@google.com>
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tools/net/bpf_dbg.c

@@ -820,7 +820,7 @@ static void bpf_single_step(struct bpf_regs *r, struct sock_filter *f,
 		r->A &= r->X;
 		break;
 	case BPF_ALU_AND | BPF_K:
-		r->A &= r->X;
+		r->A &= K;
 		break;
 	case BPF_ALU_OR | BPF_X:
 		r->A |= r->X;