pw_kvs: Move entry.h to public/pw_kvs/internal

Move entry.h so that the KeyValueStore class can reference it in the
header.

Change-Id: Ib5a7f194db8dd9af1e8f3d8c9c7c25b8409acfe0
diff --git a/pw_kvs/BUILD b/pw_kvs/BUILD
index 6adb71a..64c44b3 100644
--- a/pw_kvs/BUILD
+++ b/pw_kvs/BUILD
@@ -30,10 +30,10 @@
         "entry.cc",
         "flash_memory.cc",
         "key_value_store.cc",
+        "public/pw_kvs/internal/entry.h",
         "public/pw_kvs/internal/hash.h",
         "public/pw_kvs/internal/key_descriptor.h",
         "public/pw_kvs/internal/sector_descriptor.h",
-        "pw_kvs_private/entry.h",
         "pw_kvs_private/macros.h",
     ],
     hdrs = [