ARM: VIC: set handle_arch_irq in VIC initialization

From: Rob Herring <rob.herring at calxeda.com>

Set handle_arch_irq to vic_handle_irq. Only the first VIC initialized can
setup the handler.

Signed-off-by: Rob Herring <rob.herring at calxeda.com>
Acked-by: Olof Johansson <olof at lixom.net>