powerpc/8xxx: Fix interrupt handling in MPC8xxx GPIO driver

Interrupt handler in MPC8xxx GPIO driver is missing the call to PIC EOI
(end of interrupt) handler. As a result, at least on 85XX systems, GPIO
interrupt is delivered only once. This patch adds the missing EOI call.
Tested on custom P1022 board.
Signed-off-by: Felix Radensky <felix@embedded-sol.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

drivers/gpio/gpio-mpc8xxx.c

@@ -146,6 +146,7 @@ static int mpc8xxx_gpio_to_irq(struct gpio_chip *gc, unsigned offset)
 static void mpc8xxx_gpio_irq_cascade(unsigned int irq, struct irq_desc *desc)
 {
 	struct mpc8xxx_gpio_chip *mpc8xxx_gc = irq_desc_get_handler_data(desc);
+	struct irq_chip *chip = irq_desc_get_chip(desc);
 	struct of_mm_gpio_chip *mm = &mpc8xxx_gc->mm_gc;
 	unsigned int mask;
 
@@ -153,6 +154,7 @@ static void mpc8xxx_gpio_irq_cascade(unsigned int irq, struct irq_desc *desc)
 	if (mask)
 		generic_handle_irq(irq_linear_revmap(mpc8xxx_gc->irq,
 						     32 - ffs(mask)));
+	chip->irq_eoi(&desc->irq_data);
 }
 
 static void mpc8xxx_irq_unmask(struct irq_data *d)