sparc64: allow 64 IRQ lines

According to UltraSPARC™-IIi User’s Manual, PBM has 64 IRQ lines.

Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
sparc64: fix loosing interrupts

- clear interrupts only on writing to the interrupt clear registers
- don't overwrite a currently active interrupt request
- use the correct addresses for the interrupt clear registers
  (section 19.3.3.3 of the UltraSPARC™-IIi User’s Manual)

Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
sparc64: use direct interrupt mapping for PCI devices

Every PCI Slot in PBM has 4 directly mapped IRQ lines.
Use the IRQ routing schema 0bssnn (Bus, Slot, interrupt Number)
described in Section 19.3.3 of UltraSPARC™-IIi User's Manual.

Please note that this patch requires the OpenBIOS counterpart patch.

Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>