pdc202xx_old: wire test_irq() method for PDC2026x

In the commit e0321fbe

 (pdc202xx_old:
implement test_irq() method (take 2)) I forgot to modify
'pdc2026x_port_ops'... :-/

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>