ip6_tunnel: Match to ARPHRD_TUNNEL6 for dev type

ip6_tunnel: Match to ARPHRD_TUNNEL6 for dev type

The device type for ip6 tunnels is set to
ARPHRD_TUNNEL6. However, the ip4ip6_err function
is expecting the device type of the tunnel to be
ARPHRD_TUNNEL.  Since the device types do not
match, the function exits and the ICMP error
packet is not sent to the originating host. Note
that the device type for IPv4 tunnels is set to
ARPHRD_TUNNEL.

Fix is to expect a tunnel device type of
ARPHRD_TUNNEL6 instead.  Now the tunnel device
type matches and the ICMP error packet is sent
to the originating host.

Signed-off-by: Sheena Mira-ato <sheena.mira-ato@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>