ice: xsk: allow empty Rx descriptors on XSK ZC data path

Commit ac6f733a ("ice: allow empty Rx descriptors") stated that ice
HW can produce empty descriptors that are valid and they should be
processed.

Add this support to xsk ZC path to avoid potential processing problems.

Fixes: 2d4238f5 ("ice: Add support for AF_XDP")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/ice/ice_xsk.c

@@ -538,12 +538,18 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
 		 */
 		dma_rmb();
 
+		xdp = *ice_xdp_buf(rx_ring, rx_ring->next_to_clean);
+
 		size = le16_to_cpu(rx_desc->wb.pkt_len) &
 				   ICE_RX_FLX_DESC_PKT_LEN_M;
-		if (!size)
-			break;
+		if (!size) {
+			xdp->data = NULL;
+			xdp->data_end = NULL;
+			xdp->data_hard_start = NULL;
+			xdp->data_meta = NULL;
+			goto construct_skb;
+		}
 
-		xdp = *ice_xdp_buf(rx_ring, rx_ring->next_to_clean);
 		xsk_buff_set_size(xdp, size);
 		xsk_buff_dma_sync_for_cpu(xdp, rx_ring->xsk_pool);
 
@@ -561,7 +567,7 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
 			ice_bump_ntc(rx_ring);
 			continue;
 		}
-
+construct_skb:
 		/* XDP_PASS path */
 		skb = ice_construct_skb_zc(rx_ring, xdp);
 		if (!skb) {