net/mlx5: fix LRO checksum

net/mlx5: fix LRO checksum

The TCP checksum includes IPV4 pseudo-header checksum and L3
payload checksum which include TCP header and TCP payload.
When mlx5 LRO is enabled, HW will calculate the TCP payload
checksum, PMD need complete the IPV4 pseudo-header checksum
and the TCP header checksum.

The mlx5_lro_update_tcp_hdr function completes the TCP header
checksum, but this function using lower 4 bits of data-offset
field in TCP header to get the whole TCP header length, this
will cause TCP header checksum wrong calculation.

Update the code using higher 4 bits of data-offset field
instead of lower 4 bits.

Fixes: e4c2a16eb1de ("net/mlx5: handle LRO packets in Rx queue")
Cc: stable@dpdk.org
Signed-off-by: Dong Zhou <dongz@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>