wolfcrypt misc: avoid frivolous initialization.

Author: philljj

wolfcrypt/src/misc.c

@@ -1009,9 +1009,12 @@ WC_MISC_STATIC WC_INLINE void ato64(const byte *in, w64wrapper *w64)
 #ifdef BIG_ENDIAN_ORDER
     XMEMCPY(&w64->n, in, sizeof(w64->n));
 #else
-    word64 _in = 0;
-    XMEMCPY(&_in, in, sizeof(_in));
-    w64->n = ByteReverseWord64(_in);
+    union {
+        word64 w;
+        byte b[sizeof(word64)];
+    } _in;
+    XMEMCPY(_in.b, in, sizeof(_in));
+    w64->n = ByteReverseWord64(_in.w);
 #endif /* BIG_ENDIAN_ORDER */
 }