iwlwifi: Use PCI Express Capability accessors

Use PCI Express Capability access functions to simplify iwlwifi driver.

[bhelgaas: split iwlegacy, iwlwifi, rtlwifi into separate patches]
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/net/wireless/iwlwifi/pcie/trans.c

@@ -675,13 +675,10 @@ static void iwl_set_pwr_vmain(struct iwl_trans *trans)
 static u16 iwl_pciexp_link_ctrl(struct iwl_trans *trans)
 {
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
-	int pos;
 	u16 pci_lnk_ctl;
 
-	struct pci_dev *pci_dev = trans_pcie->pci_dev;
-
-	pos = pci_pcie_cap(pci_dev);
-	pci_read_config_word(pci_dev, pos + PCI_EXP_LNKCTL, &pci_lnk_ctl);
+	pcie_capability_read_word(trans_pcie->pci_dev, PCI_EXP_LNKCTL,
+				  &pci_lnk_ctl);
 	return pci_lnk_ctl;
 }