net/mlx5e: XDP, Improve dma address calculation of linear part for XDP_TX

net/mlx5e: XDP, Improve dma address calculation of linear part for XDP_TX

When calculating the dma address of the linear part of an XDP frame, the
formula assumes that there is a single XDP buffer per page. Extend the
formula to allow multiple XDP buffers per page by calculating the data
offset in the page.

This is a preparation for the upcoming removal of a single XDP buffer
per page limitation when the formula will no longer be correct.

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/20260403090927.139042-3-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>