MFC: r204152, r204164

MFC: r204152, r204164

Some machines can not only consist of CPUs running at different speeds
but also of different types, f.e. Sun Fire V890 can be equipped with a
mix of UltraSPARC IV and IV+ CPUs, requiring different MMU initialization
and different workarounds for model specific errata. Therefore move the
CPU implementation number from a global variable to the per-CPU data.
Functions which are called before the latter is available are passed the
implementation number as a parameter now.

git-svn-id: svn://svn.freebsd.org/base/stable/8@206005 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f