net/mlx5: Improve naming of pci function vectors

The variable pf_vec is used to denote the number of vectors required for
the pci function's own use. To avoid confusion interpreting pf as
physical function, change the name to pcif_vec.

Same reasoning goes for pf_pool which is really pci function pool.

Signed-off-by: Eli Cohen <elic@nvidia.com>
Reviewed-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>