dt-bindings: spi: sunxi: Add H616 compatible string

Add the obvious compatible name to the existing SPI binding, and pair
it with the existing H3 fallback compatible string, as the devices are
compatible.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210125151811.11871-14-andre.przywara@arm.com


Signed-off-by: Mark Brown <broonie@kernel.org>