fix: gprs_bssgp_vty: logging filter: wrong constant

Setting the BVC log filter to NULL worked only if the NSVC filter was set,
use the proper constant instead.

Change-Id: Ic1cc268ed20700698c93d3ff8bf85cc0f01d3b1b
diff --git a/src/gb/gprs_bssgp_vty.c b/src/gb/gprs_bssgp_vty.c
index 90e5001..1f382a2 100644
--- a/src/gb/gprs_bssgp_vty.c
+++ b/src/gb/gprs_bssgp_vty.c
@@ -49,7 +49,7 @@
 	if (bctx) {
 		target->filter_map |= (1 << FLT_BVC);
 		target->filter_data[FLT_BVC] = bctx;
-	} else if (target->filter_data[FLT_NSVC]) {
+	} else if (target->filter_data[FLT_BVC]) {
 		target->filter_map = ~(1 << FLT_BVC);
 		target->filter_data[FLT_BVC] = NULL;
 	}