sun4u: remove pci_ebus_init() function

sun4u: remove pci_ebus_init() function

This is initialisation that should really take place in the ebus realize
function. As part of this we also rework the ebus IRQ mapping so that
instead of having to pass in the array of pbm_irqs, we obtain a reference
to them by looking up the APB device during ebus realize.

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>