igc: Refactor igc_clean_rx_ring()

Refactor igc_clean_rx_ring() helper, preparing the code for AF_XDP
zero-copy support which is added by upcoming patches.

The refactor consists of encapsulating page-shared specific code into
its own helper, leaving common code that will be shared by both
page-shared and xsk pool in igc_clean_rx_ring().

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Signed-off-by: Vedang Patel <vedang.patel@intel.com>
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>