bssgp_bvc_fsm: Move log message to the correct place

The log message is very confusing if printed for PtP-BVCI as well. Move
it into the correct if branch.

Change-Id: I0359443ddc52108b492f741005c4699e06b40183
diff --git a/src/gb/bssgp_bvc_fsm.c b/src/gb/bssgp_bvc_fsm.c
index ce9079d..664ad09 100644
--- a/src/gb/bssgp_bvc_fsm.c
+++ b/src/gb/bssgp_bvc_fsm.c
@@ -415,8 +415,8 @@
 		rx = data;
 		tp = (const struct tlv_parsed *) msgb_bcid(rx);
 		/* If BVC-UNBLOCK-ACK PDU is received by an BSS for the signalling BVC, the PDU is ignored. */
-		LOGPFSML(fi, LOGL_ERROR, "Rx BVC-UNBLOCK-ACK on BVCI=0 is illegal\n");
 		if (bfp->bvci == 0) {
+			LOGPFSML(fi, LOGL_ERROR, "Rx BVC-UNBLOCK-ACK on BVCI=0 is illegal\n");
 			if (!bfp->role_sgsn)
 				break;
 			_tx_status(fi, BSSGP_CAUSE_SEM_INCORR_PDU, rx);