killing use of ppc_md.init

[Kumar Gala]

ppc_md.init only exists on ppc32 and seems like its pretty useless  
today.  The users seem to fall into two classes:

1. called to do of_platform_bus_probe() - most platforms use  
machine_device_initcall() for this
2. some platform init code which seems like it could move into  
setup_arch().

The second one seems to only be on amigaone and chrp.  Anyone know if  
there is any harm in moving the amigaone_init() into  
amigaone_setup_arch() and similarly on chrp chrp_init2() into  
chrp_setup_arch().

- k