gpio: sifive: To get gpio irq offset from device tree data

We can get hwirq number of the gpio by its irq_data->hwirq so that we don't
need to add more macros for different platforms. This patch is tested in
SiFive Unleashed board and SiFive Unmatched board.
Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpio-sifive.c

@@ -29,7 +29,6 @@
 #define SIFIVE_GPIO_OUTPUT_XOR	0x40
 
 #define SIFIVE_GPIO_MAX		32
-#define SIFIVE_GPIO_IRQ_OFFSET	7
 
 struct sifive_gpio {
 	void __iomem		*base;
@@ -37,7 +36,7 @@ struct sifive_gpio {
 	struct regmap		*regs;
 	unsigned long		irq_state;
 	unsigned int		trigger[SIFIVE_GPIO_MAX];
-	unsigned int		irq_parent[SIFIVE_GPIO_MAX];
+	unsigned int		irq_number[SIFIVE_GPIO_MAX];
 };
 
 static void sifive_gpio_set_ie(struct sifive_gpio *chip, unsigned int offset)
@@ -144,8 +143,12 @@ static int sifive_gpio_child_to_parent_hwirq(struct gpio_chip *gc,
 					     unsigned int *parent,
 					     unsigned int *parent_type)
 {
+	struct sifive_gpio *chip = gpiochip_get_data(gc);
+	struct irq_data *d = irq_get_irq_data(chip->irq_number[child]);
+
 	*parent_type = IRQ_TYPE_NONE;
-	*parent = child + SIFIVE_GPIO_IRQ_OFFSET;
+	*parent = irqd_to_hwirq(d);
+
 	return 0;
 }
 
@@ -165,7 +168,7 @@ static int sifive_gpio_probe(struct platform_device *pdev)
 	struct irq_domain *parent;
 	struct gpio_irq_chip *girq;
 	struct sifive_gpio *chip;
-	int ret, ngpio;
+	int ret, ngpio, i;
 
 	chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
 	if (!chip)
@@ -200,6 +203,9 @@ static int sifive_gpio_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	for (i = 0; i < ngpio; i++)
+		chip->irq_number[i] = platform_get_irq(pdev, i);
+
 	ret = bgpio_init(&chip->gc, dev, 4,
 			 chip->base + SIFIVE_GPIO_INPUT_VAL,
 			 chip->base + SIFIVE_GPIO_OUTPUT_VAL,