Add counters: pcu.bts.N.pch.requests.timeout

Implement T3113 for paging over PCH with default value of 7s (same as
T3113 in OsmoBSC). Increase the new counter on timeout.

Related: SYS#4878
Change-Id: I97475c3dbe2cf00b9cbfec39e93a3c65cb7f749f
diff --git a/src/bts.cpp b/src/bts.cpp
index 4e3b770..a96fe24 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -133,6 +133,7 @@
 	{ "llc:dl_bytes",               "RLC encapsulated PDUs"},
 	{ "llc:ul_bytes",               "full PDUs received   "},
 	{ "pch:requests",		"PCH requests sent    "},
+	{ "pch:requests:timeout",	"PCH requests timeout "},
 	{ "rach:requests",		"RACH requests received"},
 	{ "11bit_rach:requests",	"11BIT_RACH requests received"},
 	{ "spb:uplink_first_segment",   "First seg of UL SPB  "},
@@ -283,6 +284,8 @@
 
 	llist_add_tail(&bts->list, &pcu->bts_list);
 
+	INIT_LLIST_HEAD(&bts->pch_timer);
+
 	return bts;
 }