mtd: atmel_nand: change log level

PIO fall back is not an issue, so don't make this much noise.

Signed-off-by: Nicolas Ferre <[e-mail]>
Signed-off-by: Brian Norris <[e-mail]>

drivers/mtd/nand/atmel_nand.c

···
 	dma_unmap_single(dma_dev->dev, phys_addr, len, dir);
 err_buf:
 	if (err != 0)
-		dev_warn(host->dev, "Fall back to CPU I/O\n");
+		dev_dbg(host->dev, "Fall back to CPU I/O\n");
 	return err;
 }