genirq: Fix percpu_devid irq affinity documentation

Stephen points out that some of the percpu_devid irq affinity
documentation is either missing or not matching the data structures.

Address all the issues in one go.

Fixes: 87b0031 ("irqdomain: Add firmware info reporting interface")
Fixes: 258e7d2 ("genirq: Add affinity to percpu_devid interrupt requests")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://patch.msgid.link/20251030143032.2035987-1-maz@kernel.org

Author: Marc Zyngier

include/linux/interrupt.h

@@ -109,6 +109,7 @@ typedef irqreturn_t (*irq_handler_t)(int, void *);
  * @name:	name of the device
  * @dev_id:	cookie to identify the device
  * @percpu_dev_id:	cookie to identify the device
+ * @affinity:	CPUs this irqaction is allowed to run on
  * @next:	pointer to the next irqaction for shared interrupts
  * @irq:	interrupt number
  * @flags:	flags (see IRQF_* above)

include/linux/irqdomain.h

@@ -48,7 +48,7 @@ struct irq_fwspec {
  * struct irq_fwspec_info - firmware provided IRQ information structure
  *
  * @flags:		Information validity flags
- * @cpumask:		Affinity mask for this interrupt
+ * @affinity:		Affinity mask for this interrupt
  *
  * This structure reports firmware-specific information about an
  * interrupt. The only significant information is the affinity of a