hw/i386/pc: Populate RTC attribute directly

hw/i386/pc: Populate RTC attribute directly

Both the piix and the q35 machines introduce an rtc_state variable and defer the
initialization of the X86MachineState::rtc attribute to pc_cmos_init(). Resolve
this complication which makes pc_cmos_init() do what it says on the tin.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Message-ID: <20240224135851.100361-6-shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>