cappuccino: move icache to fetch
pic: ack all spr accesses, not only writes
ticktimer: ack all spr accesses, not only writes
cpu: remove unused immu spr signals
cappuccino/execute_ctrl: add mfspr stall logic (wait for ack)
dmmu: fix spr bus read acks
dpram_sclk: add single clocked dual port ram
add immu implementation

Still very rough but it passes the immu tests in or1200-mmu,
but only when icache is disabled.
Icache is virtually indexed, physically tagged when immu is
enabled, so there might be because of aliasing problem,
more investigation on this is needed.
(This is the first ever known VIPT immu/icache implementation)