ftp: use constant instead of value

[Jan Klemkow]

Hi,

This diff just swaps -2 with the actual constant to increase
readability of the ftp source code.

bye,
Jan

Index: fetch.c
===================================================================
RCS file: /cvs/src/usr.bin/ftp/fetch.c,v
retrieving revision 1.132
diff -u -p -r1.132 fetch.c
--- fetch.c     8 Oct 2014 04:01:10 -0000       1.132
+++ fetch.c     30 Oct 2014 13:53:35 -0000
@@ -1519,7 +1519,7 @@ SSL_readline(struct ressl *ssl, size_t *
                }
 again:
                ret = ressl_read(ssl, &c, 1, &nr);
-               if (ret == -2)
+               if (ret == RESSL_READ_AGAIN)
                        goto again;
                if (ret != 0)
                        errx(1, "SSL read error: %u", ret);