irqchip/gic: Correct declaration of *percpu_base pointer in union gic_base

percpu_base is used in various percpu functions that expect variable in
__percpu address space. Correct the declaration of percpu_base to

void __iomem * __percpu *percpu_base;

to declare the variable as __percpu pointer.

The patch fixes several sparse warnings:

irq-gic.c:1172:44: warning: incorrect type in assignment (different address spaces)
irq-gic.c:1172:44:    expected void [noderef] __percpu *[noderef] __iomem *percpu_base
irq-gic.c:1172:44:    got void [noderef] __iomem *[noderef] __percpu *
...
irq-gic.c:1231:43: warning: incorrect type in argument 1 (different address spaces)
irq-gic.c:1231:43:    expected void [noderef] __percpu *__pdata
irq-gic.c:1231:43:    got void [noderef] __percpu *[noderef] __iomem *percpu_base

There were no changes in the resulting object files.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/all/20241213145809.2918-2-ubizjak@gmail.com