irqchip: davinci-aintc: move the driver to drivers/irqchip

The aintc driver has now been cleaned up. Move it to drivers/irqchip
where it belongs. There's no device-tree support for any dm* board so
there's no IRQCHIP_OF_DECLARE() - there's only the exported init
function called from machine code.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>