hw/arm/armsse: Introduce SSE subsystem version property

hw/arm/armsse: Introduce SSE subsystem version property

We model Arm "Subsystems for Embedded" SoC subsystems using generic
code which is split into various sub-devices which are configurable
by QOM properties to handle the behaviour differences between the SSE
subsystems we implement.  Currently the only sub-device which needs
to change is the IOTKIT_SYSCTL device, and we do this with a mix of
properties that directly specify divergent behaviours (eg
CPUWAIT_RST) and passing it the SYS_VERSION register value as a way
for it to distinguish IoTKit from SSE-200.

The "pass SYS_VERSION" approach is already a bit hacky, since the
IOTKIT_SYSCTL device has to know that the different part of the
register value happens to be bits [31:28].  For SSE-300 this register
is renamed SOC_IDENTITY and has a different format entirely, all of
whose fields can be configured by the SoC integrator when they
integrate the SSE into their SoC, and so "pass SYS_VERSION" breaks
down completely.

Switch to using a simple integer property representing an
internal-to-QEMU enumeration of the SSE flavour.  For the moment we
only need this in IOTKIT_SYSCTL, but as we add SSE-300 support a few
of the other devices will also need to know.

We define and permit a value for the SSE-300 so we can start using
it in subsequent commits which add SSE-300 support.

The now-redundant is_sse200 flag in IoTKitSysCtl will be removed
in the following commit.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210219144617.4782-6-peter.maydell@linaro.org