genirq: Kill irq_chip::parent_device

Now that noone is using irq_chip::parent_device in the tree, get
rid of it.
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Acked-by: NBartosz Golaszewski <brgl@bgdev.pl>
Link: https://lore.kernel.org/r/20220201120310.878267-13-maz@kernel.org

include/linux/irq.h

@@ -456,7 +456,6 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
 /**
  * struct irq_chip - hardware interrupt chip descriptor
  *
- * @parent_device:	pointer to parent device for irqchip
  * @name:		name for /proc/interrupts
  * @irq_startup:	start up the interrupt (defaults to ->enable if NULL)
  * @irq_shutdown:	shut down the interrupt (defaults to ->disable if NULL)
@@ -503,7 +502,6 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
  * @flags:		chip specific flags
  */
 struct irq_chip {
-	struct device	*parent_device;
 	const char	*name;
 	unsigned int	(*irq_startup)(struct irq_data *data);
 	void		(*irq_shutdown)(struct irq_data *data);

kernel/irq/chip.c

@@ -1560,9 +1560,6 @@ int irq_chip_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 
 static struct device *irq_get_parent_device(struct irq_data *data)
 {
-	if (data->chip->parent_device)
-		return data->chip->parent_device;
-
 	if (data->domain)
 		return data->domain->dev;