Patch from David Brownell

This adds a mechanism for a per-machine initcall, one that's
guaranteed to run only to initialize a kernel running on that
specific hardware.  It's not strictly necessary, but it does
eliminate the need for certain boilerplate in machine-specific
support, to ensure it's only running on the right hardware:

      /* in arch/arm/mach-xxx/MYMACHINE.c */
      ...
      static int __init init_MYMACHINE(void)
      {
           if (!mach_is_MYMACHINE())       // often forgotten!!
                return -EINVAL;
           ... declare and customize platform devices
           ...
           return 0;
      }
      arch_initcall(init_MYMACHINE);

An init_MYMACHINE() call still exists, but it'd be declared
as part of the machine definition.