tbf_{ul,dl}_fsm: Abort on unexpected path

That path should not really happen. It happening would mean a totally wrong
code being used. Hence, just abort() to simplify the code.

Change-Id: Iaf65e909e45cc279e5be4b045c15174f910ffc12
diff --git a/src/tbf_dl_fsm.c b/src/tbf_dl_fsm.c
index 9cc2007..abcd0c4 100644
--- a/src/tbf_dl_fsm.c
+++ b/src/tbf_dl_fsm.c
@@ -60,10 +60,7 @@
 		ch = "PACCH";
 		break;
 	default:
-		LOGPTBFDL(ctx->dl_tbf, LOGL_ERROR,
-			  "attempted to %sset unexpected ass. type %d - FIXME!\n",
-			set ? "" : "un", t);
-		return;
+		OSMO_ASSERT(0);
 	}
 
 	if (set && prev_set)
diff --git a/src/tbf_ul_fsm.c b/src/tbf_ul_fsm.c
index f6615a8..5d02032 100644
--- a/src/tbf_ul_fsm.c
+++ b/src/tbf_ul_fsm.c
@@ -59,10 +59,7 @@
 		ch = "PACCH";
 		break;
 	default:
-		LOGPTBFUL(ctx->ul_tbf, LOGL_ERROR,
-			  "attempted to %sset unexpected ass. type %d - FIXME!\n",
-			  set ? "" : "un", t);
-		return;
+		OSMO_ASSERT(0);
 	}
 
 	if (set && prev_set)