bpf: use skb_pkt_type_ok helper in bpf_skb_change_type

Since we have a skb_pkt_type_ok() helper for checking the type before
mangling, make use of it instead of open coding. Follow-up to commit
8b10cab6 ("net: simplify and make pkt_type_ok() available for other
users") that came in after d2485c42 ("bpf: add bpf_skb_change_type
helper").
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/filter.c

@@ -1976,8 +1976,8 @@ static u64 bpf_skb_change_type(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 	u32 pkt_type = r2;
 
 	/* We only allow a restricted subset to be changed for now. */
-	if (unlikely(skb->pkt_type > PACKET_OTHERHOST ||
-		     pkt_type > PACKET_OTHERHOST))
+	if (unlikely(!skb_pkt_type_ok(skb->pkt_type) ||
+		     !skb_pkt_type_ok(pkt_type)))
 		return -EINVAL;
 
 	skb->pkt_type = pkt_type;