staging: greybus: Fix the irq API abuse

Nothing outside of low level architecture code is supposed to look up
interrupt descriptors and fiddle with them.

Replace the open coded abuse by calling generic_handle_irq().

This still does not explain why and in which context this connection
magic is injecting interrupts in the first place and why this is correct
and safe, but at least the API abuse is gone.

Fixes: 036aad9d ("greybus: gpio: add interrupt handling support")
Fixes: 2611ebef ("greybus: gpio: don't call irq-flow handler directly")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/87o8t9boqq.fsf@nanos.tec.linutronix.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/gpio.c

@@ -364,8 +364,7 @@ static int gb_gpio_request_handler(struct gb_operation *op)
 	struct gb_message *request;
 	struct gb_gpio_irq_event_request *event;
 	u8 type = op->type;
-	int irq;
-	struct irq_desc *desc;
+	int irq, ret;
 
 	if (type != GB_GPIO_TYPE_IRQ_EVENT) {
 		dev_err(dev, "unsupported unsolicited request: %u\n", type);
@@ -391,17 +390,15 @@ static int gb_gpio_request_handler(struct gb_operation *op)
 		dev_err(dev, "failed to find IRQ\n");
 		return -EINVAL;
 	}
-	desc = irq_to_desc(irq);
-	if (!desc) {
-		dev_err(dev, "failed to look up irq\n");
-		return -EINVAL;
-	}
 
 	local_irq_disable();
-	generic_handle_irq_desc(desc);
+	ret = generic_handle_irq(irq);
 	local_irq_enable();
 
-	return 0;
+	if (ret)
+		dev_err(dev, "failed to invoke irq handler\n");
+
+	return ret;
 }
 
 static int gb_gpio_request(struct gpio_chip *chip, unsigned int offset)