datapath: Allow jumbograms through IPv6 parsing.

datapath: Allow jumbograms through IPv6 parsing.

Currently we stop parsing packets that are IPv6 jumbograms.  While
it isn't possible to send such large packets to userspace, it's better
to drop them at that point rather than prematurely in the IPv6 code.
IPv6 does make some use of the payload length field but we can just as
easily use skb->len, which is what all other parsing uses.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>