mtd: rawnand: atmel: Fix dma_mapping_error() address

It seems like what was intended is to test if the dma_map of the
previous line failed but the wrong dma address was passed.

Fixes: f88fc12 ("mtd: nand: Cleanup/rework the atmel_nand driver")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Rule: add
Link: https://lore.kernel.org/stable/20250702064515.18145-2-fourier.thomas%40gmail.com
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: Thomas-fourier

drivers/mtd/nand/raw/atmel/nand-controller.c

@@ -373,7 +373,7 @@ static int atmel_nand_dma_transfer(struct atmel_nand_controller *nc,
 	dma_cookie_t cookie;
 
 	buf_dma = dma_map_single(nc->dev, buf, len, dir);
-	if (dma_mapping_error(nc->dev, dev_dma)) {
+	if (dma_mapping_error(nc->dev, buf_dma)) {
 		dev_err(nc->dev,
 			"Failed to prepare a buffer for DMA access\n");
 		goto err;