i40e/i40evf: Add EEE LPI stats

Add 4 new stats to keep track of EEE LPI (Low Power Idle) state.

Change-ID: Id6316619bb0559789770288b694a54d17f8fac5c
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Kevin Scott <kevin.c.scott@intel.com>
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>