usb: xhci: add a member hci_version in xhci_ctrl struct

Add a member to save xHCI version, it's used some times.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 126dabc..4be1411 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1283,6 +1283,7 @@
 
 	reg = HC_VERSION(xhci_readl(&hccr->cr_capbase));
 	printf("USB XHCI %x.%02x\n", reg >> 8, reg & 0xff);
+	ctrl->hci_version = reg;
 
 	return 0;
 }