pw_kvs: Fix shadow declarations

Renames some parameters to fix shadow declaration errors.

Change-Id: I85992b451785630ad8090fde6c662e5dbf9a39f8
diff --git a/pw_kvs/public/pw_kvs/key_value_store.h b/pw_kvs/public/pw_kvs/key_value_store.h
index 62c037d..40d31a3 100644
--- a/pw_kvs/public/pw_kvs/key_value_store.h
+++ b/pw_kvs/public/pw_kvs/key_value_store.h
@@ -223,8 +223,8 @@
     friend class iterator;
 
     constexpr Item(const KeyValueStore& kvs,
-                   const internal::EntryCache::const_iterator& iterator)
-        : kvs_(kvs), iterator_(iterator), key_buffer_{} {}
+                   const internal::EntryCache::const_iterator& item_iterator)
+        : kvs_(kvs), iterator_(item_iterator), key_buffer_{} {}
 
     void ReadKey();
 
@@ -262,9 +262,10 @@
    private:
     friend class KeyValueStore;
 
-    constexpr iterator(const KeyValueStore& kvs,
-                       const internal::EntryCache::const_iterator& iterator)
-        : item_(kvs, iterator) {}
+    constexpr iterator(
+        const KeyValueStore& kvs,
+        const internal::EntryCache::const_iterator& item_iterator)
+        : item_(kvs, item_iterator) {}
 
     Item item_;
   };