hw/display/virtio-vga: Convert TYPE_VIRTIO_VGA_BASE to 3-phase reset

hw/display/virtio-vga: Convert TYPE_VIRTIO_VGA_BASE to 3-phase reset

Convert the TYPE_VIRTIO_VGA_BASE class to 3-phase reset, so we
don't need to use device_class_set_parent_reset() any more.

Note that this is an abstract class itself; none of the subclasses
override its reset method.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20221125115240.3005559-3-peter.maydell@linaro.org