MIPS: DTS: CI20: add DT node for IR sensor

The infrared sensor on the CI20 board is connected to a GPIO and can
be operated by using the gpio-ir-recv driver. Add a DT node for the
sensor to allow that driver to be used.

Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>