Implements basic differences between XScale and plain ARM. The patch
also adds the main on-chip peripherals of PXA2xx: interrupt
controller, DMA, GPIO controller, SSP, I2C, I2S busses, UARTs, FIR
port, RTC, Clock/Power/Memory managers.

There's also an api to hook funcitons to coprocessor writes and reads
becaue PXA uses those in various on-chip peripherals (and they're
supposed to be faster than memory IO access to the same peripherals,
on the real hardware).

Cheers,
Andrew