net/mlx5e: RX, Prepare non-linear striding RQ for XDP multi-buffer support

In preparation for supporting XDP multi-buffer in striding RQ, use
xdp_buff struct to describe the packet. Make its skb_shared_info collide
the one of the allocated SKB, then add the fragments using the xdp_buff
API.

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