gsm_bts: add version and variant details

* add version string to gsm_bts
* add PCU version string to gsm_bts
* rename GSM_BTS_TYPE_OSMO_SYSMO -> GSM_BTS_OSMOBTS to avoid confusion
  between BTS model and variant
* add variant enum to gsm_bts_model using enum with variants for each
  hw vendor of OsmoBTS
* show connected PCU version (if available) in vty via 'show bts'

This will come in handy when logging details regarding particular BTS
reported via OML, see:

Related: OS#1614

Change-Id: I6710d53115f34634a7b70969cc05fd5c72ff8ab2
diff --git a/openbsc/src/libcommon/gsm_data.c b/openbsc/src/libcommon/gsm_data.c
index 3e12430..fd34793 100644
--- a/openbsc/src/libcommon/gsm_data.c
+++ b/openbsc/src/libcommon/gsm_data.c
@@ -96,7 +96,7 @@
 	{ GSM_BTS_TYPE_NANOBTS,	"nanobts" },
 	{ GSM_BTS_TYPE_RBS2000,	"rbs2000" },
 	{ GSM_BTS_TYPE_NOKIA_SITE, "nokia_site" },
-	{ GSM_BTS_TYPE_OSMO_SYSMO, "sysmobts" },
+	{ GSM_BTS_TYPE_OSMOBTS,	"sysmobts" },
 	{ 0,			NULL }
 };
 
@@ -106,7 +106,7 @@
 	{ GSM_BTS_TYPE_NANOBTS,		"ip.access nanoBTS or compatible" },
 	{ GSM_BTS_TYPE_RBS2000,		"Ericsson RBS2000 Series" },
 	{ GSM_BTS_TYPE_NOKIA_SITE,	"Nokia {Metro,Ultra,In}Site" },
-	{ GSM_BTS_TYPE_OSMO_SYSMO,	"sysmocom sysmoBTS" },
+	{ GSM_BTS_TYPE_OSMOBTS,		"sysmocom sysmoBTS" },
 	{ 0,				NULL }
 };
 
@@ -274,7 +274,7 @@
 
 	switch (bts->type) {
 	case GSM_BTS_TYPE_NANOBTS:
-	case GSM_BTS_TYPE_OSMO_SYSMO:
+	case GSM_BTS_TYPE_OSMOBTS:
 		/* Set the default OML Stream ID to 0xff */
 		bts->oml_tei = 0xff;
 		bts->c0->nominal_power = 23;