irqchip: omap-intc: Fix support for dm814 and dm816

On dm81xx we have 128 interrupts like am33xx has. Let's add
compatible flags for dm814x and dm816x, and document the
existing binding.

As the dm81xx are booting in device tree only mode, we can now
also remove ti81xx_init_irq() legacy function.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Cc: Brian Hutchinson <b.hutchman@gmail.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1421187806-6804-2-git-send-email-tony@atomide.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>