kconfig: rename file_write_dep and move it to confdata.c

file_write_dep() is called only from conf_write_autoconf().
Move it from util.c to confdata.c to make it static.
Also, rename it to conf_write_dep() since it should belong to
the group of conf_write* functions.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/lkc.h

@@ -97,7 +97,6 @@ void menu_set_type(int type);
 
 /* util.c */
 struct file *file_lookup(const char *name);
-int file_write_dep(const char *name);
 void *xmalloc(size_t size);
 void *xcalloc(size_t nmemb, size_t size);
 void *xrealloc(void *p, size_t size);