io-util: move fputs_with_newline to fileio

Follow-up for cdf6f34a2f

We already have other fputs()-like helpers in fileio rather than
io-util. While at it, switch the order of params.

src/core/unit.c

@@ -33,7 +33,6 @@
 #include "format-util.h"
 #include "id128-util.h"
 #include "install.h"
-#include "io-util.h"
 #include "iovec-util.h"
 #include "label-util.h"
 #include "load-dropin.h"
@@ -4570,9 +4569,9 @@ int unit_write_setting(Unit *u, UnitWriteFlags flags, const char *name, const ch
         }
 
         if (u->transient_file) {
-                /* When this is a transient unit file in creation, then let's not create a new drop-in but instead
-                 * write to the transient unit file. */
-                fputs_with_newline(data, u->transient_file);
+                /* When this is a transient unit file in creation, then let's not create a new drop-in,
+                 * but instead write to the transient unit file. */
+                fputs_with_newline(u->transient_file, data);
 
                 /* Remember which section we wrote this entry to */
                 u->last_section_private = !!(flags & UNIT_PRIVATE);