Fix the wrong block found when doing split_region

uc.c

@@ -1198,11 +1198,13 @@ static bool split_region(struct uc_struct *uc, MemoryRegion *mr,
         return false;
     }
 
+    // Find the correct and large enough (which contains our target mr)
+    // to create the content backup.
     QLIST_FOREACH(block, &uc->ram_list.blocks, next)
     {
         // block->offset is the offset within ram_addr_t, not GPA
         if (block->mr->addr <= mr->addr &&
-            block->used_length >= (mr->end - mr->addr)) {
+            block->used_length + block->mr->addr >= mr->end) {
             break;
         }
     }