Don't include <machine/cputypes.h> or declare cputype/class interfaces

Don't include <machine/cputypes.h> or declare cputype/class interfaces
in <machine/cpu.h>.  Moved the declarations to <machine/cputypes.h>.
Fixed style bugs in the moved code.  Fixed everything that depended on
the nested include.  Don't include <machine/cpu.h> (in the changed files)
unless something in it is used directly.