USB DFU bootloader blocked because of RFM95 module (DIO5)

[jeandet]

There is no pull down resistor on RFM95 reset pin and DIO5 by default is clkout, this prevent the MCU to enter DFU mode generating a lot of:

[268721.923613] usb 5-3-port4: attempt power cycle
[268722.526763] usb 5-3.4: new full-speed USB device number 111 using xhci_hcd
[268722.526854] usb 5-3.4: Device not responding to setup address.
[268722.731529] usb 5-3.4: Device not responding to setup address.
[268722.938996] usb 5-3.4: device not accepting address 111, error -71
[268723.015776] usb 5-3.4: new full-speed USB device number 112 using xhci_hcd
[268723.015881] usb 5-3.4: Device not responding to setup address.
[268723.219173] usb 5-3.4: Device not responding to setup address.
[268723.426869] usb 5-3.4: device not accepting address 112, error -71
[268723.427205] usb 5-3-port4: unable to enumerate USB device

The simplest solution is to disconnect this pin which should be useless.