tbf: Update FSM names when TFI change during tbf_update()

In that function, previous PDCHs are unlinked and then alloc_algorithm
is expected to assign new TFIs.

Change-Id: I7bcbb223ca32400bede7ab638695ba3c015c9946

src/tbf.cpp

@@ -334,6 +334,8 @@ int gprs_rlcmac_tbf::update()
 			dl_tbf->set_window_size();
 	}
 
+	tbf_update_state_fsm_name(this);
+
 	return 0;
 }