bts: Add a flag to remember the kind of activation/release

When the PCU is activating a channel we don't want to tell the
BSC using RSL. Add a flag so we can keep track of who asked for
the activation/release of the channel.

openbsc/include/openbsc/gsm_data_shared.h

@@ -296,6 +296,8 @@ struct gsm_lchan {
 	} ho;
 	/* S counter for link loss */
 	int s;
+	/* Kind of the release/activation. E.g. RSL or PCU */
+	int rel_act_kind;
 #endif
 };