net/mlx5: Fix setting number of EQs of SFs

When setting number of completion EQs of the SF, consider number of
online CPUs.
Without this consideration, when number of online cpus are less than 8,
unnecessary 8 completion EQs are allocated.

Fixes: c36326d3

 ("net/mlx5: Round-Robin EQs over IRQs")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>