irqchip: remove davinci aintc driver

The aintc driver was used on Davinci DM3xx and DM64xx SoCs, all of
which got dropped from Linux, so this driver is orphaned as well.

Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>