Implement support for receiving BSSMAP CommonID from MSC

The MSC may at any time send a BSSMAP CommonID message via a
SCCP connection to inform us of the IMSI of the subscriber.  Let's
make use of that information by associating a related bsc_subscr
and updating the identity of the bsc_subscr_conn_fsm for improved
logging / filtering.

Closes: OS#2969
Change-Id: I52c43fb940f0db796adf4c0adb2260321c721c39
diff --git a/include/osmocom/bsc/bsc_msc_data.h b/include/osmocom/bsc/bsc_msc_data.h
index b1fe14d..43ace25 100644
--- a/include/osmocom/bsc/bsc_msc_data.h
+++ b/include/osmocom/bsc/bsc_msc_data.h
@@ -64,6 +64,7 @@
 	MSC_CTR_BSSMAP_RX_DT1_HANDOVER_CMD,
 	MSC_CTR_BSSMAP_RX_DT1_CLASSMARK_RQST,
 	MSC_CTR_BSSMAP_RX_DT1_CONFUSION,
+	MSC_CTR_BSSMAP_RX_DT1_COMMON_ID,
 	MSC_CTR_BSSMAP_RX_DT1_UNKNOWN,
 	MSC_CTR_BSSMAP_RX_DT1_DTAP,
 	MSC_CTR_BSSMAP_RX_DT1_DTAP_ERROR,