util: only close fds larger than -1 in cleanup_close

This allows us to pass xerrno() results (i.e. negative errnos) and still
do the right thing.

Assisted-by: Claude:claude-opus-4-6
Part-of: <https://gitlab.freedesktop.org/libinput/libei/-/merge_requests/388>

src/util-io.h

@@ -127,7 +127,7 @@ xerrno(int value)
 static inline int
 xclose(int fd)
 {
-	if (fd != -1) {
+	if (fd > -1) {
 		/* Not SYSCALL(), see libei MR!261#note_2131802 */
 		close(fd);
 	}