apb: remove pci_apb_init() and instantiate APB device using qdev

apb: remove pci_apb_init() and instantiate APB device using qdev

By making the special_base and mem_base values qdev properties, we can move
the remaining parts of pci_apb_init() into the pbm init() and realize()
functions.

This finally allows us to instantiate the APB directly using standard qdev
create/init functions in sun4u.c.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Artyom Tarasenko <atar4qemu@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>