hw/arm/raspi: Avoid using TypeInfo::class_data pointer

Using class_data pointer to create a MachineClass is not
the recommended way anymore. The correct way is to open-code
the MachineClass::fields in the class_init() method.

We can not use TYPE_RASPI_MACHINE::class_base_init() because
it is called *before* each machine class_init(), therefore the
board_rev field is not populated. We have to manually call
raspi_machine_class_common_init() for each machine.

This partly reverts commit a03bde36.

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20200924111808.77168-5-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>