fix building broken in r1578

src/os/unix/ngx_process_cycle.c

diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
index 7d7ef79..4705f39 100644
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -1035,7 +1035,6 @@
 ngx_channel_handler(ngx_event_t *ev)
 {
     ngx_int_t          n;
-    ngx_socket_t       fd;
     ngx_channel_t      ch;
     ngx_connection_t  *c;