dt-bindings: irq: sun7i-nmi: fix dt-binding for a80 nmi

There is no one use "allwinner,sun9i-a80-sc-nmi". The A80 uses
"allwinner,sun9i-a80-nmi".

Let's fix it.

Signed-off-by: Yangtao Li <frank@allwinnertech.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/fb081585c4fedcb9b8b95e5f16879dff482c9717.1595572867.git.frank@allwinnertech.com