net/netvsc: fix calculation of checksums based on mbuf flag

net/netvsc: fix calculation of checksums based on mbuf flag

The netvsc should use RTE_MBUF_F_TX_L4_MASK and check the masked value
to decide the correct way to calculate checksums.

Not checking for RTE_MBUF_F_TX_L4_MASK results in incorrect RNDIS
packets sent to VSP and incorrect checksums calculated by the VSP.

Fixes: 4e9c73e96e ("net/netvsc: add Hyper-V network device")
Cc: stable@dpdk.org
Signed-off-by: Long Li <longli@microsoft.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Ferruh Yigit <ferruh.yigit@xilinx.com>