igc: Introduce igc_rx_buffer_flip() helper

The igc driver implements the same page recycling scheme from other
Intel drivers which reuses the page by flipping the buffer. The code
to handle buffer flips is duplicated in many locations so introduce
the igc_rx_buffer_flip() helper and use it where applicable.

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>