thunderbolt: Check router generation before connecting xHCI

Only Thunderbolt 3 routers need the xHCI connection flow. This also
ensures the router actually has both lane adapters (1 and 3). While
there move declaration of the boolean variables inside the block where
they are being used.

Fixes: 30a4eca6 ("thunderbolt: Add internal xHCI connect flows for Thunderbolt 3 devices")
Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/switch.c

@@ -3786,14 +3786,18 @@ int tb_switch_pcie_l1_enable(struct tb_switch *sw)
  */
 int tb_switch_xhci_connect(struct tb_switch *sw)
 {
-	bool usb_port1, usb_port3, xhci_port1, xhci_port3;
 	struct tb_port *port1, *port3;
 	int ret;
 
+	if (sw->generation != 3)
+		return 0;
+
 	port1 = &sw->ports[1];
 	port3 = &sw->ports[3];
 
 	if (tb_switch_is_alpine_ridge(sw)) {
+		bool usb_port1, usb_port3, xhci_port1, xhci_port3;
+
 		usb_port1 = tb_lc_is_usb_plugged(port1);
 		usb_port3 = tb_lc_is_usb_plugged(port3);
 		xhci_port1 = tb_lc_is_xhci_connected(port1);