debug: Make GPRS params non-const to avoid compiler warning

Make log_set_nsvc_filter, log_set_bvc_filter take a non-const
parameter as we are going to assign it to a non-const pointer.
diff --git a/openbsc/src/debug.c b/openbsc/src/debug.c
index 2a67398..512935a 100644
--- a/openbsc/src/debug.c
+++ b/openbsc/src/debug.c
@@ -222,8 +222,7 @@
 	}
 }
 
-void log_set_nsvc_filter(struct log_target *target,
-			 const struct gprs_nsvc *nsvc)
+void log_set_nsvc_filter(struct log_target *target, struct gprs_nsvc *nsvc)
 {
 	if (nsvc) {
 		target->filter_map |= (1 << FLT_NSVC);
@@ -234,8 +233,7 @@
 	}
 }
 
-void log_set_bvc_filter(struct log_target *target,
-			const struct bssgp_bvc_ctx *bctx)
+void log_set_bvc_filter(struct log_target *target, struct bssgp_bvc_ctx *bctx)
 {
 	if (bctx) {
 		target->filter_map |= (1 << FLT_BVC);