malloc: refactored aligned_OK and misaligned_chunk

Renamed aligned_OK to misaligned_mem as to be similar
to misaligned_chunk, and reversed any assertions using
the macro.  Made misaligned_chunk call misaligned_mem after
chunk2mem rather than bitmasking with the malloc alignment
itself, since misaligned_chunk is meant to test the data
chunk itself rather than the header, and the compiler
will optimise the addition so the ternary operator is not
needed.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

malloc/malloc-check.c

@@ -111,7 +111,7 @@ mem2chunk_check (void *mem, unsigned char **magic_p)
   INTERNAL_SIZE_T sz, c;
   unsigned char magic;
 
-  if (!aligned_OK (mem))
+  if (misaligned_mem (mem))
     return NULL;
 
   p = mem2chunk (mem);