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

mainline inclusion
from mainline-5.3-rc1
commit 19c36b18
category: bugfix
bugzilla: 23209
CVE: NA

-------------------------------------------------

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: NMarc Zyngier <marc.zyngier@arm.com>
Acked-by: NMark Rutland <mark.rutland@ar.com>
Signed-off-by: NJulien Thierry <julien.thierry@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWei Li <liwei391@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.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");
 }