net/mlx5: fix DevX scattered Rx queue size

net/mlx5: fix DevX scattered Rx queue size

The WQ size configuration via DevX didn't take into account the maximum
number of segments per packet what wrongly caused to configure bigger
WQE size than the size expected by the PMD in other places.

The scatter mode stride size should be the size of segment multiplied
by the number of maximum segments per packet.
The number of WQEs per WQ should be the number of descriptors divided by
the number of the maximum segments per packet.

Fix the size calculations to the above rule.

Fixes: dc9ceff73c99 ("net/mlx5: create advanced RxQ via DevX")

Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>