Use OSMO_FD_* instead of deprecated BSC_FD_*

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_* symbols when
copy-pasting somewhere else.

Change-Id: Ida8fd3bd7347163567acde34ad67aefee913b0ea
diff --git a/src/osmo-bts-sysmo/sysmo_l1_hw.c b/src/osmo-bts-sysmo/sysmo_l1_hw.c
index 8351d68..a67e875 100644
--- a/src/osmo-bts-sysmo/sysmo_l1_hw.c
+++ b/src/osmo-bts-sysmo/sysmo_l1_hw.c
@@ -163,7 +163,7 @@
 	read_ofd->priv_nr = q;
 	read_ofd->data = hdl;
 	read_ofd->cb = l1if_fd_cb;
-	read_ofd->when = BSC_FD_READ;
+	read_ofd->when = OSMO_FD_READ;
 	rc = osmo_fd_register(read_ofd);
 	if (rc < 0) {
 		close(read_ofd->fd);
@@ -182,7 +182,7 @@
 	write_ofd->fd = rc;
 	write_ofd->priv_nr = q;
 	write_ofd->data = hdl;
-	write_ofd->when = BSC_FD_WRITE;
+	write_ofd->when = OSMO_FD_WRITE;
 	rc = osmo_fd_register(write_ofd);
 	if (rc < 0) {
 		close(write_ofd->fd);