Address mapping PPC 405

[Peter Ryser]

>Since there is no seperate IO memory space you can access the registers
>with simple pointers.
>
>Whether or not it is a good idea (based on coding conventions) I'll
>leave for someone else to answer.  :)
>
You want to use the read{b,w,l} and write{b,w,l} macros for two reasons:
1. Accesses to registers need to be synch'ed with 'eieio' or some other 
synchronizing instructions.
2. Portability of your driver if you ever should ever move it to a 
different architecture and/or change the endianness in your system

- Peter