drivers: serial: silabs: Fix uart tx abort at high baudrate

At high baudrate when using async api of the uart, the abort
function in not giving the right informations since we're stopping
the dma after getting the status of it. It makes the uart_async_api test
failed on high baudrate.

Signed-off-by: Martin Hoff <martin.hoff@silabs.com>

Author: Martinhoff-maker

drivers/serial/uart_silabs_usart.c

@@ -539,11 +539,12 @@ static int uart_silabs_async_tx_abort(const struct device *dev)
 	USART_IntClear(config->base, USART_IF_TXC | USART_IF_TCMP2);
 	(void)uart_silabs_pm_lock_put(dev, UART_SILABS_PM_LOCK_TX);
 
+	dma_stop(data->dma_tx.dma_dev, data->dma_tx.dma_channel);
+
 	if (!dma_get_status(data->dma_tx.dma_dev, data->dma_tx.dma_channel, &stat)) {
 		data->dma_tx.counter = tx_buffer_length - stat.pending_length;
 	}
 
-	dma_stop(data->dma_tx.dma_dev, data->dma_tx.dma_channel);
 	data->dma_tx.enabled = false;
 
 	async_evt_tx_abort(data);