Also correctly report device disconnection if Upstream polls too slowly.
Conflicts:
Downstream/Src/downstream_statemachine.c
Upstream/Middlewares/ST/STM32_USB_Device_Library/Class/MSC/Src/usbd_msc_scsi.c
with Downstream project.
Also fixed a couple of things in upstream_spi.c and
upstream_interface_msc.c but due to file rename the diff is not
obvious...