i40e: remove unnecessary cleaned_count updates

For performance reasons, remove the redundant updates of the cleaned_count
variable, as its value can be computed based on the ring next-to-clean
variable, which is consistently updated.

Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>