dt-bindings: interrupt-controller: New binding for the meson sm1 SoCs

Update the dt-binding to add support for the sm1 SoC family in the
amlogic GPIO interrupt controller driver.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20190829161635.25067-2-jbrunet@baylibre.com