e1_input: Support I.460 timeslot type

Unlike the legacy TRAU mode, this only adds I460 mux/demux,
without any TRAU frame synchronization.  The user must still be
adding the actual sub-channels using osmo_i460_subchan_add()
depending on his requirements.

Change-Id: I44da6dfec77ef475adb35001a0e4fa11d549aa02
diff --git a/src/input/e1d.c b/src/input/e1d.c
index e3a3b82..3ae1d89 100644
--- a/src/input/e1d.c
+++ b/src/input/e1d.c
@@ -310,7 +310,8 @@
 e1d_want_write(struct e1inp_ts *e1i_ts)
 {
         /* We never include the DAHDI B-Channel FD into the writeset */
-	if (e1i_ts->type == E1INP_TS_TYPE_TRAU) {
+	if (e1i_ts->type == E1INP_TS_TYPE_TRAU ||
+	    e1i_ts->type == E1INP_TS_TYPE_I460) {
 		LOGPITS(e1i_ts, DLINP, LOGL_DEBUG, "Trying to write TRAU ts\n");
 		return 0;
 	}
@@ -429,6 +430,7 @@
 			bfd->when = OSMO_FD_READ;
 			break;
 		case E1INP_TS_TYPE_TRAU:
+		case E1INP_TS_TYPE_I460:
 		case E1INP_TS_TYPE_RAW:
 			/* close/release LAPD instance, if any */
 			if (e1i_ts->lapd) {