soc_term.py: write to stdout not stdin

The serv_conn() function should write the data read from the connection
to stdout, not stdin. Although stdin appears to work when soc_term is
invoked from a terminal in an interactive session, things get bad when
trying to redirect its output:

 $ ./soc_term 54320 | tee nsec.log
 <... make run etc. ...>
 ^C
 $ file nsec.log
 nsec.log: empty

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/soc_term.py b/soc_term.py
index c40362b..5178b60 100755
--- a/soc_term.py
+++ b/soc_term.py
@@ -99,7 +99,7 @@
                 buf = bytearray(data)
                 handle_telnet_codes(readyfd, buf)
                 if (readyfd == fd):
-                    to = sys.stdin.fileno()
+                    to = sys.stdout.fileno()
                 else:
                     to = fd
             except ConnectionResetError: