hw/char/stm32f2xx_usart: Do not update data register when device is disabled

When the device is disabled, the internal circuitry keeps the data
register loaded and doesn't update it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20190104182057.8778-1-philmd@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
1 file changed