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/basic/fileio.h

@@ -144,6 +144,7 @@ int write_timestamp_file_atomic(const char *fn, usec_t n);
 int read_timestamp_file(const char *fn, usec_t *ret);
 
 int fputs_with_separator(FILE *f, const char *s, const char *separator, bool *space);
+int fputs_with_newline(FILE *f, const char *s);
 
 typedef enum ReadLineFlags {
         READ_LINE_ONLY_NUL  = 1 << 0,