hw/arm/armsse: Make number of SRAM banks parameterised

hw/arm/armsse: Make number of SRAM banks parameterised

The SSE-200 has four banks of SRAM, each with its own
Memory Protection Controller, where the IoTKit has only one.
Make the number of SRAM banks a field in ARMSSEInfo.

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-id: 20190121185118[email protected]