object-name.h: move declarations for object-name.c functions from cache.h

Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/submodule-config.c b/submodule-config.c
index ecf0fcf..252b90a 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -9,6 +9,7 @@
 #include "submodule-config.h"
 #include "submodule.h"
 #include "strbuf.h"
+#include "object-name.h"
 #include "object-store.h"
 #include "parse-options.h"
 #include "tree-walk.h"