Remove unreachable assignments

This is harmless, but we might as well remove the unreachable line. If we
ever add a break to the loop and we don't think of changing the surrounding
code, it would make more sense not to set exit_code to SUCCESS.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

programs/ssl/ssl_fork_server.c

@@ -357,8 +357,6 @@ int main(void)
         goto exit;
     }
 
-    exit_code = MBEDTLS_EXIT_SUCCESS;
-
 exit:
     mbedtls_net_free(&client_fd);
     mbedtls_net_free(&listen_fd);