gprs_bssgp_pcu: add comments to the pcu states

Related: OS#3879
Change-Id: Iccf6508ce46162e6dfd6b00abd44e24cb425b346
diff --git a/src/gprs_bssgp_pcu.h b/src/gprs_bssgp_pcu.h
index db77cbb..6c6de1d 100644
--- a/src/gprs_bssgp_pcu.h
+++ b/src/gprs_bssgp_pcu.h
@@ -53,10 +53,14 @@
 
 	struct osmo_timer_list bvc_timer;
 
+	/* state: is the NSVC unblocked? */
 	int nsvc_unblocked;
 
+	/* state: true if bvc signalling needs to be reseted or waiting for reset ack */
 	int bvc_sig_reset;
+	/* state: true if bvc ptp needs to be reseted or waiting for reset ack */
 	int bvc_reset;
+	/* state: true if bvc ptp is unblocked */
 	int bvc_unblocked;
 
 	/* Flow control */