Convert the TI-NSPIRE interrupt controller binding to schema format.
It's a straight-forward conversion of the typical interrupt controller.
'#interrupt-cells' was missing from the property list, but used in the
example, so add it.
Link: https://lore.kernel.org/r/20250505144711.1289677-1-robh@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
