mfd: sm501: Fix potential NULL pointer dereference

There is a potential NULL pointer dereference in case devm_kzalloc()
fails and returns NULL.

Fix this by adding a NULL check on *lookup*

This bug was detected with the help of Coccinelle.

Fixes: b2e63555 ("i2c: gpio: Convert to use descriptors")
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/sm501.c

@@ -1145,6 +1145,9 @@ static int sm501_register_gpio_i2c_instance(struct sm501_devdata *sm,
 	lookup = devm_kzalloc(&pdev->dev,
 			      sizeof(*lookup) + 3 * sizeof(struct gpiod_lookup),
 			      GFP_KERNEL);
+	if (!lookup)
+		return -ENOMEM;
+
 	lookup->dev_id = "i2c-gpio";
 	if (iic->pin_sda < 32)
 		lookup->table[0].chip_label = "SM501-LOW";