vmxnet3: segCnt can be 1 for LRO packets

The device emulation may send segCnt of 1 for LRO packets.

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>