Allow Convb in backend.

[r15835]

ir/ir/irvrfy.c

@@ -1525,7 +1525,8 @@ static int verify_node_Conv(ir_node *n, ir_graph *irg) {
 	(void) irg;
 
 	ASSERT_AND_RET_DBG(
-		mode_is_datab(op1mode) && mode_is_data(mymode),
+		get_irg_phase_state(irg) == phase_backend ||
+		(mode_is_datab(op1mode) && mode_is_data(mymode)),
 		"Conv node", 0,
 		show_unop_failure(n, "/* Conv: BB x datab --> data */");
 	);