[POWERPC] Move inline asm eieio to using eieio inline function

Use the eieio function so we can redefine what eieio does rather
than direct inline asm.  This is part code clean up and partially
because not all PPCs have eieio (book-e has mbar that maps to eieio).

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/asm-powerpc/system.h b/include/asm-powerpc/system.h
index 09621f6..eff3de9 100644
--- a/include/asm-powerpc/system.h
+++ b/include/asm-powerpc/system.h
@@ -43,7 +43,7 @@
 #ifdef CONFIG_SMP
 #define smp_mb()	mb()
 #define smp_rmb()	rmb()
-#define smp_wmb()	__asm__ __volatile__ ("eieio" : : : "memory")
+#define smp_wmb()	eieio()
 #define smp_read_barrier_depends()	read_barrier_depends()
 #else
 #define smp_mb()	barrier()