MINOR: ebtree: save 8 bytes in struct eb32sc_node

There is a 4-bytes hole in this structure after the eb_node and the
last field is 4-bytes as well, resulting in a total of 64 bytes with
8 bytes holes. Just moving the key after the eb_node (like in eb32_node)
fills the hole and reduces the structure's size by 8 bytes.

ebtree/eb32sctree.h

@@ -41,9 +41,9 @@ typedef   signed int s32;
  */
 struct eb32sc_node {
 	struct eb_node node; /* the tree node, must be at the beginning */
+	u32 key;
 	unsigned long node_s; /* visibility of this node's branches */
 	unsigned long leaf_s; /* visibility of this node's leaf */
-	u32 key;
 };
 
 /*