bssgp_tx_bvc_unblock(): Fix log message

We're transmitting a BVC-UNBLOCK but the log states the opposite:
BVC-BLOCK.  Let's fix that.

Change-Id: I70fa7336402d193513f89fcf3068b0b21925702d
diff --git a/src/gb/gprs_bssgp_bss.c b/src/gb/gprs_bssgp_bss.c
index bef9bb1..f06c403 100644
--- a/src/gb/gprs_bssgp_bss.c
+++ b/src/gb/gprs_bssgp_bss.c
@@ -277,7 +277,7 @@
 			(struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
 	uint16_t _bvci = osmo_htons(bctx->bvci);
 
-	LOGP(DBSSGP, LOGL_NOTICE, "BSSGP (BVCI=%u) Tx BVC-BLOCK\n", bctx->bvci);
+	LOGP(DBSSGP, LOGL_NOTICE, "BSSGP (BVCI=%u) Tx BVC-UNBLOCK\n", bctx->bvci);
 
 	msgb_nsei(msg) = bctx->nsei;
 	msgb_bvci(msg) = 0; /* Signalling */