util/rb_tree: Reverse the order of comparison functions

The new order matches that of the comparison functions accepted by the C
standard library qsort() functions.  Being consistent with qsort will
hopefully help avoid developer confusion.

The only current user of the red-black tree is aub_mem.c which is pretty
easy to fix up.

Reviewed-by: Lionel Landwerlin <lionel.g.lndwerlin@intel.com>

src/intel/tools/aub_mem.c

@@ -87,9 +87,9 @@ static inline int
 cmp_uint64(uint64_t a, uint64_t b)
 {
    if (a < b)
-      return -1;
-   if (a > b)
       return 1;
+   if (a > b)
+      return -1;
    return 0;
 }