[media] media: rc: meson: document device tree bindings

This adds binding documentation for the infrared remote control
receiver available in Amlogic Meson SoCs.

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>