Driver: Vmxnet3: set CHECKSUM_UNNECESSARY for IPv6 packets

Driver: Vmxnet3: set CHECKSUM_UNNECESSARY for IPv6 packets

BugLink: http://bugs.launchpad.net/bugs/1605494
For IPv6, if the device indicates that the checksum is correct, set
CHECKSUM_UNNECESSARY.

Reported-by: Subbarao Narahari <snarahari@vmware.com>
Signed-off-by: Shrikrishna Khare <skhare@vmware.com>
Signed-off-by: Jin Heo <heoj@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(back ported from commit f0d437809d23999cb25207cfbe80c61e5703fdc1)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
 Conflicts:
	drivers/net/vmxnet3/vmxnet3_int.h

Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>