usb: xhci-pci: Drop non-DM version of xhci-pci driver

As there is no board that currently uses xhci-pci driver without DM
USB, drop its support and leave only DM support.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
index 9edc589..67ad72b 100644
--- a/drivers/usb/host/Kconfig
+++ b/drivers/usb/host/Kconfig
@@ -33,6 +33,7 @@
 
 config USB_XHCI_PCI
 	bool "Support for PCI-based xHCI USB controller"
+	depends on DM_USB
 	default y if X86
 	help
 	  Enables support for the PCI-based xHCI controller.