libavformat/network: use defined constant in poll

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/network.c

@@ -75,7 +75,7 @@ int ff_network_wait_fd(int fd, int write)
     int ev = write ? POLLOUT : POLLIN;
     struct pollfd p = { .fd = fd, .events = ev, .revents = 0 };
     int ret;
-    ret = poll(&p, 1, 100);
+    ret = poll(&p, 1, POLLING_TIME);
     return ret < 0 ? ff_neterrno() : p.revents & (ev | POLLERR | POLLHUP) ? 0 : AVERROR(EAGAIN);
 }