irqchip/gic-v3: Fix __iomem warning

irqchip/gic-v3: Fix __iomem warning

The __iomem attribute should go before the * in the
prototype. Move to silence the following sparse
warnings:

./arch/arm/include/asm/arch_gicv3.h:340:15: warning: incorrect type in argument 1 (different address spaces)
./arch/arm/include/asm/arch_gicv3.h:340:15:    expected void const volatile [noderef] <asn:2> *addr
./arch/arm/include/asm/arch_gicv3.h:340:15:    got void *
./arch/arm/include/asm/arch_gicv3.h:343:17: warning: incorrect type in argument 2 (different address spaces)
./arch/arm/include/asm/arch_gicv3.h:343:17:    expected void volatile [noderef] <asn:2> *addr
./arch/arm/include/asm/arch_gicv3.h:343:17:    got void *
./arch/arm/include/asm/arch_gicv3.h:350:37: warning: incorrect type in argument 2 (different address spaces)
./arch/arm/include/asm/arch_gicv3.h:350:37:    expected void volatile [noderef] <asn:2> *addr
./arch/arm/include/asm/arch_gicv3.h:350:37:    got void *[noderef] <asn:2> addr
drivers/irqchip/irq-gic-v3-its.c:2832:46: warning: incorrect type in argument 2 (different address spaces)
drivers/irqchip/irq-gic-v3-its.c:2832:46:    expected void *[noderef] <asn:2> addr
drivers/irqchip/irq-gic-v3-its.c:2832:46:    got void [noderef] <asn:2> *
./arch/arm/include/asm/arch_gicv3.h:340:15: warning: incorrect type in argument 1 (different address spaces)
./arch/arm/include/asm/arch_gicv3.h:340:15:    expected void const volatile [noderef] <asn:2> *addr
./arch/arm/include/asm/arch_gicv3.h:340:15:    got void *
./arch/arm/include/asm/arch_gicv3.h:343:17: warning: incorrect type in argument 2 (different address spaces)
./arch/arm/include/asm/arch_gicv3.h:343:17:    expected void volatile [noderef] <asn:2> *addr
./arch/arm/include/asm/arch_gicv3.h:343:17:    got void *
./arch/arm/include/asm/arch_gicv3.h:350:37: warning: incorrect type in argument 2 (different address spaces)
./arch/arm/include/asm/arch_gicv3.h:350:37:    expected void volatile [noderef] <asn:2> *addr
./arch/arm/include/asm/arch_gicv3.h:350:37:    got void *[noderef] <asn:2> addr

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191017113341.13778-1-ben.dooks@codethink.co.uk