mtd: nand: atmel: Fix potential NULL pointer dereference

There is a potential execution path in which function
of_find_compatible_node() returns NULL. In such a case,
we end up having a NULL pointer dereference when accessing
pointer *nfc_np* in function of_clk_get().

So, we better don't take any chances and fix this by null
checking pointer *nfc_np* before calling of_clk_get().

Addresses-Coverity-ID: 1473052 ("Dereference null return value")
Fixes: f88fc12 ("mtd: nand: Cleanup/rework the atmel_nand driver")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
Acked-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
[tudor.ambarus@microchip.com: backport to 4.14]
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>

Author: ambarus

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

@@ -2073,6 +2073,10 @@ atmel_hsmc_nand_controller_legacy_init(struct atmel_hsmc_nand_controller *nc)
 	nand_np = dev->of_node;
 	nfc_np = of_find_compatible_node(dev->of_node, NULL,
 					 "atmel,sama5d3-nfc");
+	if (!nfc_np) {
+		dev_err(dev, "Could not find device node for sama5d3-nfc\n");
+		return -ENODEV;
+	}
 
 	nc->clk = of_clk_get(nfc_np, 0);
 	if (IS_ERR(nc->clk)) {