warnings: fix alignment warnings

These warnings are for architectures that do not
support non-aligned word access.

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>

src/helper/types.h

@@ -80,7 +80,7 @@ typedef bool _Bool;
  */
 #define container_of(ptr, type, member) ({			\
 	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
-	(type *)( (char *)__mptr - offsetof(type,member) );})
+	(type *)( (void *) ( (char *)__mptr - offsetof(type,member) ) );})
 
 
 /**