USBx DFU module has been updated for FORCE_DISCONNET event

[GodavarthyAravinda]

Issue

USBx DFU module has been updated to prevent 'USB remove event' being called twice when executing USB disconnection.

Workaround

This change requires application(s) to be updated in DFU callback to check DETACH state in FORCE_DISCONNECT event. Please see the example code:

 UINT usbx_status_callback (ULONG status)
 {
    UX_SLAVE_CLASS_DFU * dfu;
    UCHAR                state;
    switch (status)
    {
        case UX_DEVICE_ATTACHED:
        {
            tx_event_flags_set(&g_cdcacm_event_flags0, CDCACM_FLAG, TX_OR);
            break;
        }
        case UX_DEVICE_REMOVED:
        {
            tx_event_flags_set(&g_cdcacm_event_flags0, ~CDCACM_FLAG, TX_AND);
            break;
        }
        case UX_DEVICE_FORCE_DISCONNECT:
        {
            state = ux_device_class_dfu_state_get(dfu);
            if ((UX_SYSTEM_DFU_STATE_APP_DETACH == state) ||
                (UX_SYSTEM_DFU_STATE_DFU_MANIFEST_WAIT_RESET == state))
            {
                tx_event_flags_set(&g_cdcacm_event_flags0, DFU_DETACH_REQUEST_FLAG, TX_OR);
            }

            break;
        }

        default:
        {
            /* do nothing */
            break;
        }
    }

    return 0;
}