arm64: irqflags: Pass flags as readonly operand to restore instruction

Flags are only read by the instructions doing the irqflags restore
operation. Pass the operand as read only to the asm inline instead of
read-write.

Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Mark Rutland <mark.rutland@ar.com>
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/irqflags.h

@@ -119,8 +119,8 @@ static inline void arch_local_irq_restore(unsigned long flags)
 			__msr_s(SYS_ICC_PMR_EL1, "%0")
 			"dsb	sy",
 			ARM64_HAS_IRQ_PRIO_MASKING)
-		: "+r" (flags)
 		:
+		: "r" (flags)
 		: "memory");
 }