powerpc: Fix hard_irq_disable() with sanitizer

As reported by Zhouyi Zhou, WRITE_ONCE() is not atomic
as expected when KASAN or KCSAN are compiled in.

Fix it by re-implementing it using inline assembly.

Fixes: 077fc62 ("powerpc/irq: remove inline assembly in hard_irq_disable macro")
Reported-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a8298991b3df049a54ee8e558838e34265812014.1661272586.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/hw_irq.h

@@ -282,7 +282,8 @@ static inline bool pmi_irq_pending(void)
 	flags = irq_soft_mask_set_return(IRQS_ALL_DISABLED);		\
 	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;			\
 	if (!arch_irqs_disabled_flags(flags)) {				\
-		WRITE_ONCE(local_paca->saved_r1, current_stack_pointer);\
+		asm volatile("std%X0 %1,%0" : "=m" (local_paca->saved_r1) \
+					    : "r" (current_stack_pointer)); \
 		trace_hardirqs_off();					\
 	}								\
 } while(0)