i40e: Add a new variable to track number of pf instances

Track the number of physical functions (PFs) found, this is a global counter
on purpose so that each pf loaded has a unique ID.

Change-Id: I74d618520afbce4a774d0235449e3b5f97ff6d4a
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>