powerpc: Fix alignment for AltiVec multilibs

cpukit/score/cpu/powerpc/rtems/score/powerpc.h

@@ -72,8 +72,6 @@ extern "C" {
 #define CPU_MODEL_NAME "Generic (classic FPU)"
 #endif
 
-#define PPC_ALIGNMENT			8
-
 #ifdef __PPC_CPU_E6500__
 #define PPC_DEFAULT_CACHE_LINE_POWER 6
 #else
@@ -136,6 +134,12 @@ extern "C" {
 #define PPC_MULTILIB_FPU
 #endif
 
+#ifdef PPC_MULTILIB_ALTIVEC
+#define PPC_ALIGNMENT 16
+#else
+#define PPC_ALIGNMENT 8
+#endif
+
 /*
  *  Unless specified above, If the model has FP support, it is assumed to
  *  support doubles (8-byte floating point numbers).