datapath: Account for "udp: Generic functions to set checksum"

datapath: Account for "udp: Generic functions to set checksum"

Upstream commit:
    udp: Generic functions to set checksum

    Added udp_set_csum and udp6_set_csum functions to set UDP checksums
    in packets. These are for simple UDP packets such as those that might
    be created in UDP tunnels.

    Signed-off-by: Tom Herbert <therbert@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Upstream: af5fcba7 ("udp: Generic functions to set checksum")
Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Thomas Graf <tgraf@noironetworks.com>