From Matthew Dobson.

This final patch from Matthew cleans up a few leftovers which were noted
after the code had been reviewed and tested a bit in the -mm patchsets.

1) Update register_XXX and arch_register_XXX functions to return int
   instead of void.  Functions calling these functions should know if
   they completed successfully to take appropriate further registration
   action, or not bother.

2) Drop some pointless error checking in the arch_register_XXX
   functions.