To ensure lowest possible power consumption when the peripheral is not needed, stop and disable UARTE.
The DMA.TX.STOP and DMA.RX.STOP tasks are not always needed (the peripheral might already be stopped). If DMA.TX.STOP or DMA.RX.STOP is sent, software waits until the TXSTOPPED or RXTO event is received before disabling the peripheral through the ENABLE register.