geneve: fix incorrect setting of UDP checksum flag

Creating a geneve link with 'udpcsum' set results in a creation of link
for which UDP checksum will NOT be computed on outbound packets, as can
be seen below.

11: gen0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN
    link/ether c2:85:27:b6:b4:15 brd ff:ff:ff:ff:ff:ff promiscuity 0
    geneve id 200 remote 192.168.13.1 dstport 6081 noudpcsum

Similarly, creating a link with 'noudpcsum' set results in a creation
of link for which UDP checksum will be computed on outbound packets.

Fixes: 9b4437a5 ("geneve: Unify LWT and netdev handling.")
Signed-off-by: Girish Moodalbail <girish.moodalbail@oracle.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Acked-by: Lance Richardson <lrichard@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>