Use OSMO_FD_* instead of deprecated BSC_FD_*

New define is available since libosmocore 1.1.0, and we already require
1.1.0, so no need to update dependenices.
Let's change it to avoid people re-using old BSC_FD_* symbols when
copy-pasting somewhere else.

Change-Id: I9b6463af713f76c06a144bdbf202c0d91eef4d21
diff --git a/src/libosmo-mgcp-client/mgcp_client.c b/src/libosmo-mgcp-client/mgcp_client.c
index b6bf43b..74bdf4d 100644
--- a/src/libosmo-mgcp-client/mgcp_client.c
+++ b/src/libosmo-mgcp-client/mgcp_client.c
@@ -829,7 +829,7 @@
 	mgcp->remote_addr = htonl(addr.sin_addr.s_addr);
 
 	osmo_wqueue_init(wq, 1024);
-	wq->bfd.when = BSC_FD_READ;
+	wq->bfd.when = OSMO_FD_READ;
 	wq->bfd.data = mgcp;
 	wq->read_cb = mgcp_do_read;
 	wq->write_cb = mgcp_do_write;