net/mlx5e: Enable reporting checksum unnecessary also for L3 packets

We can report checksum unnecessary also when the L3 checksum
flag on the cqe is set and there's no L4 header.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>