PCI: Use pci_find_vsec_capability() when looking for TBT devices

Currently set_pcie_thunderbolt() open-codes pci_find_vsec_capability().
Refactor the former to use the latter. No functional change intended.

Link: https://lore.kernel.org/r/20211115112902.24033-1-andriy.shevchenko@linux.intel.comSigned-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Krzysztof Wilczyński <kw@linux.com>

drivers/pci/probe.c

@@ -1579,20 +1579,12 @@ void set_pcie_hotplug_bridge(struct pci_dev *pdev)
 
 static void set_pcie_thunderbolt(struct pci_dev *dev)
 {
-	int vsec = 0;
-	u32 header;
-
-	while ((vsec = pci_find_next_ext_capability(dev, vsec,
-						    PCI_EXT_CAP_ID_VNDR))) {
-		pci_read_config_dword(dev, vsec + PCI_VNDR_HEADER, &header);
+	u16 vsec;
 
 	/* Is the device part of a Thunderbolt controller? */
-		if (dev->vendor == PCI_VENDOR_ID_INTEL &&
-		    PCI_VNDR_HEADER_ID(header) == PCI_VSEC_ID_INTEL_TBT) {
+	vsec = pci_find_vsec_capability(dev, PCI_VENDOR_ID_INTEL, PCI_VSEC_ID_INTEL_TBT);
+	if (vsec)
 		dev->is_thunderbolt = 1;
-			return;
-		}
-	}
 }
 
 static void set_pcie_untrusted(struct pci_dev *dev)