net/mlx5e: Introduce extended version for mlx5e_xmit_data

Introduce struct mlx5e_xmit_data_frags to be used for non-linear xmit
buffers. Let it include sinfo pointer.

Take one bit from the len field to indicate if the descriptor has
fragments and can be casted-up into the extended version.

Zero-init to make sure has_frags, and potentially future fields, are
zero when not explicitly assigned.

Another field will be added in a downstream patch to indicate and point
to dma addresses of the different frags, for redirect-in requests.

This simplifies the mlx5e_xmit_xdp_frame/mlx5e_xmit_xdp_frame_mpwqe
functions params.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>