dt-bindings: optee driver interrupt can be a per-cpu interrupt

Explicit in optee firmware device tree bindings that the interrupt
used by optee driver for async notification can be a peripheral
interrupt or a per-cpu interrupt.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>