mfd: tps65910: Fix possible invalid pointer dereference on regmap_add_irq_chip fail

Fixes: 4aab3fadad32 ("mfd: tps65910: Move interrupt implementation code to mfd file")

tps65910_irq_init() sets 'tps65910->chip_irq' before calling
regmap_add_irq_chip(). If the regmap_add_irq_chip() call fails in
memory allocation of regmap_irq_chip_data members then:

1. The 'tps65910->chip_irq' will still hold some value
2. 'tps65910->irq_data' will be pointing to already freed memory
   (because regmap_add_irq_chip() will free it on error)

This results in invalid memory access during driver remove because the
tps65910_irq_exit() tests whether 'tps65910->chip_irq' is not zero.

Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/tps65910.c

@@ -255,8 +255,10 @@ static int tps65910_irq_init(struct tps65910 *tps65910, int irq,
 	ret = regmap_add_irq_chip(tps65910->regmap, tps65910->chip_irq,
 		IRQF_ONESHOT, pdata->irq_base,
 		tps6591x_irqs_chip, &tps65910->irq_data);
-	if (ret < 0)
+	if (ret < 0) {
 		dev_warn(tps65910->dev, "Failed to add irq_chip %d\n", ret);
+		tps65910->chip_irq = 0;
+	}
 	return ret;
 }