MdeModulePkg/UsbBusDxe: Return error when the device is not present
Until now, during the USB device enumeration when its PortState
USB_PORT_STAT_CONNECTION bit was not set, the stack was not informed
that the device is not present. Fix that by returning appropriate
error code.
Signed-off-by: Marcin Wojtas <mw@semihalf.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Hao A Wu <hao.a.wu@intel.com>