eth: mlx4: create a page pool for Rx

Create a pool per rx queue. Subsequent patches will make use of it.

Move fcs_del to a hole to make space for the pointer.

Per common "wisdom" base the page pool size on the ring size.
Note that the page pool cache size is in full pages, so just
round up the effective buffer size to pages.

Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20250213010635.1354034-2-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>