mGicNumInterrupts is the total number of interrupts, so the interrupt
ID equal to mGicNumInterrupts is also invalid.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>