i40e: Fix wrong check for I40E_TXR_FLAGS_WB_ON_ITR

The I40E_TXR_FLAGS_WB_ON_ITR is i40e_ring flag and not i40e_pf one.

Fixes: 8e0764b4 ("i40e/i40evf: Add support for writeback on ITR feature for X722")
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20231023212714.178032-1-jacob.e.keller@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -2854,7 +2854,7 @@ int i40e_napi_poll(struct napi_struct *napi, int budget)
 		return budget;
 	}
 
-	if (vsi->back->flags & I40E_TXR_FLAGS_WB_ON_ITR)
+	if (q_vector->tx.ring[0].flags & I40E_TXR_FLAGS_WB_ON_ITR)
 		q_vector->arm_wb_state = false;
 
 	/* Exit the polling mode, but don't re-enable interrupts if stack might