net/mlx5e: XDP, Use a single linear page per rq

net/mlx5e: XDP, Use a single linear page per rq

Currently in striding rq there is one mlx5e_frag_page member per WQE for
the linear page. This linear page is used only in XDP multi-buffer mode.
This is wasteful because only one linear page is needed per rq: the page
gets refreshed on every packet, regardless of WQE. Furthermore, it is
not needed in other modes (non-XDP, XDP single-buffer).

This change moves the linear page into its own structure (struct
mlx5_mpw_linear_info) and allocates it only when necessary.

A special structure is created because an upcoming patch will extend
this structure to support fragmentation of the linear page.

This patch has no functional changes.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260403090927.139042-5-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>