irqchip: omap-intc: remove unnecesary of_address_to_resource() call

of_iomap(), which is called from omap_init_irq_of(),
already takes care of making sure we have a valid
resource to deal with. Because of that, we can
safely remove our explicit call to of_address_to_resource().

Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>