Use OSMO_FD_READ instead of deprecated BSC_FD_READ

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

Change-Id: I868baf575b77c448b3115701e70d439de89b0fb3
diff --git a/Transceiver52M/osmo-trx.cpp b/Transceiver52M/osmo-trx.cpp
index 9f625eb..9fcbda5 100644
--- a/Transceiver52M/osmo-trx.cpp
+++ b/Transceiver52M/osmo-trx.cpp
@@ -236,7 +236,7 @@
 		exit(EXIT_FAILURE);
 	}
 
-	osmo_fd_setup(&signal_ofd, sfd, BSC_FD_READ, signalfd_callback, NULL, 0);
+	osmo_fd_setup(&signal_ofd, sfd, OSMO_FD_READ, signalfd_callback, NULL, 0);
 	if (osmo_fd_register(&signal_ofd) < 0) {
 		fprintf(stderr, "osmo_fd_register() failed.\n");
 		exit(EXIT_FAILURE);