powerpc/64: Fix smp_wmb barrier definition use use lwsync consistently

BugLink: http://bugs.launchpad.net/bugs/1768429

commit 0bfdf598 upstream.

asm/barrier.h is not always included after asm/synch.h, which meant
it was missing __SUBARCH_HAS_LWSYNC, so in some files smp_wmb() would
be eieio when it should be lwsync. kernel/time/hrtimer.c is one case.

__SUBARCH_HAS_LWSYNC is only used in one place, so just fold it in
to where it's used. Previously with my small simulator config, 377
instances of eieio in the tree. After this patch there are 55.

Fixes: 46d075be ("powerpc: Optimise smp_wmb")
Cc: stable@vger.kernel.org # v2.6.29+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/powerpc/include/asm/barrier.h

@@ -38,7 +38,8 @@
 
 #define osb()   asm volatile("ori 31,31,0")
 
-#ifdef __SUBARCH_HAS_LWSYNC
+/* The sub-arch has lwsync */
+#if defined(__powerpc64__) || defined(CONFIG_PPC_E500MC)
 #    define SMPWMB      LWSYNC
 #else
 #    define SMPWMB      eieio

arch/powerpc/include/asm/synch.h

@@ -5,10 +5,6 @@
 #include <linux/stringify.h>
 #include <asm/feature-fixups.h>
 
-#if defined(__powerpc64__) || defined(CONFIG_PPC_E500MC)
-#define __SUBARCH_HAS_LWSYNC
-#endif
-
 #ifndef __ASSEMBLY__
 extern unsigned int __start___lwsync_fixup, __stop___lwsync_fixup;
 extern void do_lwsync_fixups(unsigned long value, void *fixup_start,