DM USB: xHCI: refine the USB disconnect logic in DM

On certain SOC, during the system suspend and resume process, connecting
and disconnecting events may happen. In previous implementation, DM didn't
clear PED bit in the xHCI PORTSC register, this will induce many invalid
polling operations in UOS and fail to enumerate one or more USB devices.

Tracked-On: #1589
Signed-off-by: Xiaoguang Wu <xiaoguang.wu@intel.com>
Reviewed-by: Liang Yang <liang3.yang@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>

Author: xiaoguangwu

devicemodel/hw/pci/xhci.c

@@ -1032,7 +1032,7 @@ pci_xhci_change_port(struct pci_xhci_vdev *xdev, int port, int usb_speed,
 
 	reg = XHCI_PORTREG_PTR(xdev, port);
 	if (conn == 0) {
-		reg->portsc &= ~XHCI_PS_CCS;
+		reg->portsc &= ~(XHCI_PS_CCS | XHCI_PS_PED);
 		reg->portsc |= (XHCI_PS_CSC |
 				XHCI_PS_PLS_SET(UPS_PORT_LS_RX_DET));
 	} else {