powerpc: Optimise smp_wmb

Change 2d1b2027626d5151fff8ef7c06ca8e7876a1a510 ("powerpc: Fixup
lwsync at runtime") removed __SUBARCH_HAS_LWSYNC, causing smp_wmb to
revert back to eieio for all CPUs.  This restores the behaviour
intorduced in 74f0609526afddd88bef40b651da24f3167b10b2 ("powerpc:
Optimise smp_wmb on 64-bit processors").

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/include/asm/system.h b/arch/powerpc/include/asm/system.h
index d6648c1..917f515 100644
--- a/arch/powerpc/include/asm/system.h
+++ b/arch/powerpc/include/asm/system.h
@@ -45,14 +45,14 @@
 #ifdef CONFIG_SMP
 
 #ifdef __SUBARCH_HAS_LWSYNC
-#    define SMPWMB      lwsync
+#    define SMPWMB      LWSYNC
 #else
 #    define SMPWMB      eieio
 #endif
 
 #define smp_mb()	mb()
 #define smp_rmb()	rmb()
-#define smp_wmb()	__asm__ __volatile__ (__stringify(SMPWMB) : : :"memory")
+#define smp_wmb()	__asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
 #define smp_read_barrier_depends()	read_barrier_depends()
 #else
 #define smp_mb()	barrier()