media: dt: bindings: Add binding for tango HW IR decoder

Add DT binding for the HW IR decoder embedded in SMP86xx/SMP87xx.

Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>