usb: device_next: msc: STALL OUT when waiting for reset

Mass Storage Class allows device to either silently discard OUT endpoint
data after receiving invalid CBW or to STALL the OUT endpoint (and keep
it STALLed regardless of host clearing halt) until Reset Recovery.

Switch from silently discarding to STALL in order to allow host realize
that device waits for Reset Recovery without transferring complete OUT
data.

Signed-off-by: Tomasz Moń <tomasz.mon@nordicsemi.no>