bts: add function to check if a BTS has a BSC co located PCU

At the momemnt we use is_ericsson_bts() to check if the BTS uses a BSC
co-located PCU, this is a bit ambiguous, lets have a function that
explicitly checks for a BSC co-located PCU and nothing else.

Change-Id: I23ed4219e5ebd188867c17f387ca877efa9bc3b0
Related: OS#5198

include/osmocom/bsc/bts.h

@@ -751,6 +751,18 @@ static inline bool is_e1_bts(const struct gsm_bts *bts)
 	return false;
 }
 
+static inline bool bsc_co_located_pcu(const struct gsm_bts *bts)
+{
+	switch (bts->type) {
+	case GSM_BTS_TYPE_RBS2000:
+		return true;
+	default:
+		break;
+	}
+
+	return false;
+}
+
 static inline const struct osmo_location_area_id *bts_lai(struct gsm_bts *bts)
 {
 	static struct osmo_location_area_id lai;

src/osmo-bsc/timeslot_fsm.c

@@ -341,7 +341,7 @@ static void ts_fsm_unused_pdch_act(struct osmo_fsm_inst *fi)
 		return;
 	}
 
-	if (is_ericsson_bts(bts) && !pcu_connected(bts)) {
+	if (bsc_co_located_pcu(bts) && !pcu_connected(bts)) {
 		LOG_TS(ts, LOGL_DEBUG, "PCU not connected: not activating PDCH.\n");
 		return;
 	}