mlxsw: pci: Initialize page pool per CQ

mlxsw: pci: Initialize page pool per CQ

Next patch will use page pool to allocate buffers for RDQ. Initialize
page pool for each CQ, which is mapped 1:1 to RDQ. Page pool for each Rx
queue enhances Rx side performance by reclaiming buffers back to each queue
specific pool.

When only one NAPI instance is the consumer of pages from page pool, it is
recommended to pass it as part of 'page_pool_params', then page pool APIs
will be done without special locks. mlxsw driver holds NAPI instance per
CQ, so add page pool per CQ and use the existing NAPI instance.

For now, pages are not allocated from the pool, next patch will use it.

Some notes regarding 'page_pool_params':
* Use PP_FLAG_DMA_MAP to allow page pool handles DMA mapping, for now
  do not use sync flag, as only the device writes to this memory and we
  read it only when it finishes writing there. This will probably be
  changed when we will support XDP.
* Define 'order' according to maximum MTU and take into account software
  overhead. Some round up are done, which means that we allocate more pages
  than we really need. This can be improved later by using fragmented
  buffers.
* Use pool_size = MLXSW_PCI_WQE_COUNT. This will be the size of 'ptr_ring',
  and should be the maximum amount of packets that page pool will allocate
  memory for. In our case, this is the queue size, defined as
  MLXSW_PCI_WQE_COUNT.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/02e5856ae7c572d4293ce6bb92c286ee6cfec800.1718709196.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>