wireguard: bump to 1.0.20200712

wireguard: bump to 1.0.20200712

This release brings parity with the commits Linus released a few hours
ago into 5.8-rc5.

* receive: account for napi_gro_receive never returning GRO_DROP

The napi_gro_receive function no longer returns GRO_DROP ever, making
handling GRO_DROP dead code. This commit removes that dead code.
Further, it's not even clear that device drivers have any business in
taking action after passing off received packets; that's arguably out of
their hands.

* device: implement header_ops->parse_protocol for AF_PACKET

WireGuard uses skb->protocol to determine packet type, and bails out if
it's not set or set to something it's not expecting. For AF_PACKET
injection, we need to support its call chain of:

    packet_sendmsg -> packet_snd -> packet_parse_headers ->
      dev_parse_header_protocol -> parse_protocol

Without a valid parse_protocol, this returns zero, and wireguard then
rejects the skb. So, this wires up the ip_tunnel handler for layer 3
packets for that case.

* queueing: make use of ip_tunnel_parse_protocol

Now that wg_examine_packet_protocol has been added for general
consumption as ip_tunnel_parse_protocol, it's possible to remove
wg_examine_packet_protocol and simply use the new
ip_tunnel_parse_protocol function directly.

* compat: backport ip_tunnel_parse_protocol and ip_tunnel_header_ops

These are required for moving wg_examine_packet_protocol out of
wireguard and into upstream.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>