libc/stdlib/nano-mallocr.c, typo in variable name

Nano malloc uses `size' in assertation whereas the correct variable would be
`s'.  Given this has existed ever since nano malloc support was added, based
on the context ("returned payload area of desired size does not exceed the
actual allocated chunk") I presume that indeed `s' (user input) and not
`r->size' (computed) shall be used.

newlib/libc/stdlib/nano-mallocr.c

@@ -396,7 +396,7 @@ void * nano_malloc(RARG malloc_size_t s)
         *(long *)((char *)r + offset) = -offset;
     }
 
-    assert(align_ptr + size <= (char *)r + alloc_size);
+    assert(align_ptr + s <= (char *)r + alloc_size);
     return align_ptr;
 }
 #endif /* DEFINE_MALLOC */