Add ocf_cache_has_pending_requests() function

Signed-off-by: Robert Baldyga <robert.baldyga@intel.com>

inc/ocf_cache.h

@@ -179,6 +179,13 @@ bool ocf_cache_is_running(ocf_cache_t cache);
  */
 void ocf_cache_wait_for_io_finish(ocf_cache_t cache);
 
+/**
+ * @brief Check if cache has any unfunished requests
+ *
+ * @param[in] cache Cache object
+ */
+bool ocf_cache_has_pending_requests(ocf_cache_t cache);
+
 /**
  * @brief Get cache mode of given cache object
  *