CLEANUP: cache: remove unused struct

Remove unused structure which remain from old dev.
diff --git a/include/types/cache.h b/include/types/cache.h
index b7e6e58..55f3503 100644
--- a/include/types/cache.h
+++ b/include/types/cache.h
@@ -1,12 +1,6 @@
 #ifndef _TYPES_CACHE_H
 #define _TYPES_CACHE_H
 
-struct cache_obj {
-	int exp;   /* expire time */
-	int etag;  /* e-tag entry */
-	int last;  /* last entry */
-	void *buf;  /* ptr to buffer */
-}
 
 #endif /*_TYPES_CACHE_H */