mncc: re-add lchan members to structs

The lchan related struct members do not serve any useful purpose
in the msc code, since the lchan concept is not in the scope of
osmo-msc. However, if removed te struct size will change which
will lead into shortened protocol messages as well. This is
is detected by osmo-sip-connector and eventually leads into
a reject ofthe shortended protocol messages.

Re add the missing struct members in order to maintain
compatibility

This commit reverts the changes made to mncc.h by commit:
e2f24d53e4f80b34ec6d656d93127cb598229a96

Change-Id: Ia02373a36df7605507ee3de49173a9fd6547b726
diff --git a/include/osmocom/msc/mncc.h b/include/osmocom/msc/mncc.h
index 881e041..49f0c8b 100644
--- a/include/osmocom/msc/mncc.h
+++ b/include/osmocom/msc/mncc.h
@@ -155,6 +155,9 @@
 	int		notify; /* 0..127 */
 	int		emergency;
 	char		imsi[16];
+
+	unsigned char	lchan_type;
+	unsigned char	lchan_mode;
 };
 
 struct gsm_data_frame {
@@ -176,6 +179,7 @@
 	uint32_t	called_offset;
 	uint32_t	signal_offset;
 	uint32_t	emergency_offset;
+	uint32_t	lchan_type_offset;
 };
 
 struct gsm_mncc_rtp {