mtd: nand: realtek-ecc: Fix a IS_ERR() vs NULL bug in probe

The dma_alloc_noncoherent() function doesn't return error pointers, it
returns NULL on error.  Fix the error checking to match.

Fixes: 3148d0e ("mtd: nand: realtek-ecc: Add Realtek external ECC engine support")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: Dan Carpenter

drivers/mtd/nand/ecc-realtek.c

@@ -418,8 +418,8 @@ static int rtl_ecc_probe(struct platform_device *pdev)
 
 	rtlc->buf = dma_alloc_noncoherent(dev, RTL_ECC_DMA_SIZE, &rtlc->buf_dma,
 					  DMA_BIDIRECTIONAL, GFP_KERNEL);
-	if (IS_ERR(rtlc->buf))
-		return PTR_ERR(rtlc->buf);
+	if (!rtlc->buf)
+		return -ENOMEM;
 
 	rtlc->dev = dev;
 	rtlc->engine.dev = dev;