net: increase maximum frame size to accomediate VLAN packets

Ethernet packages with IEEE 802.1Q VLAN support may be up to 1522
bytes long. Increase the default size used to allocate packet
storage by 4 bytes. While at it, let git care about history and
rewrite the comment to represent the situation today only.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>