powerpc: Use generic atomic64_t implementation on 32-bit processors

This makes 32-bit powerpc use the generic atomic64_t implementation.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index eae0c2b..9fb344d 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -125,6 +125,7 @@
 	select USE_GENERIC_SMP_HELPERS if SMP
 	select HAVE_OPROFILE
 	select HAVE_SYSCALL_WRAPPERS if PPC64
+	select GENERIC_ATOMIC64 if PPC32
 
 config EARLY_PRINTK
 	bool