spi: atmel-quadspi: Fix printed error code during DMA setup

On dma_request_chan() failure driver NULL-ifies the 'rx_chan' and
immediately uses it as PTR_ERR() so dev_err_probe() prints incorrect
error code.  Rework the code so proper error code will be printed and
NULL-ifying of 'rx_chan' will happen in common error handling block
(failure of DMA setup is not fatal for the driver and further code
depends on 'rx_chan' being non-NULL for DMA operations).

Reported by Smatch:
  drivers/spi/atmel-quadspi.c:1287 atmel_qspi_dma_init() warn: passing zero to 'PTR_ERR'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250501-n-smatch-fixes-v2-1-d2ad9c1f2e67@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: krzk

drivers/spi/atmel-quadspi.c

@@ -1287,9 +1287,9 @@ static int atmel_qspi_dma_init(struct spi_controller *ctrl)
 
 	aq->rx_chan = dma_request_chan(&aq->pdev->dev, "rx");
 	if (IS_ERR(aq->rx_chan)) {
-		aq->rx_chan = NULL;
-		return dev_err_probe(&aq->pdev->dev, PTR_ERR(aq->rx_chan),
-				     "RX DMA channel is not available\n");
+		ret = dev_err_probe(&aq->pdev->dev, PTR_ERR(aq->rx_chan),
+				    "RX DMA channel is not available\n");
+		goto null_rx_chan;
 	}
 
 	aq->tx_chan = dma_request_chan(&aq->pdev->dev, "tx");
@@ -1310,8 +1310,9 @@ static int atmel_qspi_dma_init(struct spi_controller *ctrl)
 
 release_rx_chan:
 	dma_release_channel(aq->rx_chan);
-	aq->rx_chan = NULL;
 	aq->tx_chan = NULL;
+null_rx_chan:
+	aq->rx_chan = NULL;
 	return ret;
 }