This enables us to remove the static array mapping in the ISA IRQ
handler (and the embedded reference to the APB device) by formalising
the interrupt wiring via the qdev GPIO API.
For more clarity we replace the APB OBIO interrupt numbers with constants
designating the interrupt source, and rename isa_irq_handler() to
ebus_isa_irq_handler().
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>