hw/arm/armsse: Add a define for number of IRQs used by the SSE itself

hw/arm/armsse: Add a define for number of IRQs used by the SSE itself

The SSE uses 32 interrupts for its own devices, and then passes through
its expansion IRQ inputs to the CPU's interrupts 33 and upward.
Add a define for the number of IRQs the SSE uses for itself, instead
of hardcoding 32.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210219144617.4782-23-peter.maydell@linaro.org