add gsm48_pdisc_names and gsm48_pdisc_name()

I often want to log the protocol discriminator in the openbsc debug log. It's
more useful to get the name directly instead of looking it up every time.

Change-Id: I0f053e2a4360b27ffccda7cf82469fb1b1cbb3ae
diff --git a/src/gsm/gsm48.c b/src/gsm/gsm48.c
index b626f82..d408897 100644
--- a/src/gsm/gsm48.c
+++ b/src/gsm/gsm48.c
@@ -678,3 +678,22 @@
 	else
 		return n_pag_blocks * (chan_desc->bs_pa_mfrms + 2);
 }
+
+const struct value_string gsm48_pdisc_names[] = {
+	OSMO_VALUE_STRING(GSM48_PDISC_GROUP_CC),
+	OSMO_VALUE_STRING(GSM48_PDISC_BCAST_CC),
+	OSMO_VALUE_STRING(GSM48_PDISC_PDSS1),
+	OSMO_VALUE_STRING(GSM48_PDISC_CC),
+	OSMO_VALUE_STRING(GSM48_PDISC_PDSS2),
+	OSMO_VALUE_STRING(GSM48_PDISC_MM),
+	OSMO_VALUE_STRING(GSM48_PDISC_RR),
+	OSMO_VALUE_STRING(GSM48_PDISC_MM_GPRS),
+	OSMO_VALUE_STRING(GSM48_PDISC_SMS),
+	OSMO_VALUE_STRING(GSM48_PDISC_SM_GPRS),
+	OSMO_VALUE_STRING(GSM48_PDISC_NC_SS),
+	OSMO_VALUE_STRING(GSM48_PDISC_LOC),
+	OSMO_VALUE_STRING(GSM48_PDISC_EXTEND),
+	OSMO_VALUE_STRING(GSM48_PDISC_MASK),
+	OSMO_VALUE_STRING(GSM48_PDISC_USSD),
+	{ 0, NULL }
+};
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 8d28476..60f83de 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -217,6 +217,7 @@
 gsm48_mcc_mnc_from_bcd;
 gsm48_chan_mode_names;
 gsm_chan_t_names;
+gsm48_pdisc_names;
 
 gsm_7bit_decode;
 gsm_7bit_decode_ussd;