hw/misc/a9scu: Do not allow invalid CPU count

Per the datasheet (DDI0407 r2p0):

  "The SCU connects one to four Cortex-A9 processors to
   the memory system through the AXI interfaces."

Change the instance_init() handler to a device_realize()
one so we can verify the property is in range, and return
an error to the caller if not.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200901144100.116742-2-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
1 file changed