net/mlx5e: Alloc rq drop page based on calculated page_shift

net/mlx5e: Alloc rq drop page based on calculated page_shift

An upcoming patch will allow setting the page order for RX
pages to be greater than 0. Make sure that the drop page will
also be allocated with the right size when that happens.

Take extra care when calculating the drop page size to
account for page_shift < PAGE_SHIFT which can happen for xsk.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260223204155.1783580-11-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>