[NET]: netdevice.h: be'ify packet_type

Everybody does

	struct packet_type foo_packet_type = {
		.type = __constant_htons(ETH_P_FOO);
	};

5 introduced warnings will be properly fixed later.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>