e1_inp: Use HDLC mode for signalling, not SIGN

The SIGN mode implies that LAPD instances are bound to the timeslots, which is
of course not what we want in a pure capturing/recording scenario.

Instead, use the new E1INP_TS_TYPE_HDLC mode, which allows us to capture
any HDLC framed messages on E1/T1 timeslots, whether LAPD or e.g. MTP.
diff --git a/src/e1_recorder.c b/src/e1_recorder.c
index 868d95d..703a67e 100644
--- a/src/e1_recorder.c
+++ b/src/e1_recorder.c
@@ -16,7 +16,7 @@
 	switch (ts->type) {
 	case E1INP_TS_TYPE_RAW:
 		return OSMO_E1CAP_MODE_RAW;
-	case E1INP_TS_TYPE_SIGN:
+	case E1INP_TS_TYPE_HDLC:
 		return OSMO_E1CAP_MODE_HDLC;
 	case E1INP_TS_TYPE_TRAU:
 		return OSMO_E1CAP_MODE_TRAU;