MFC: r203830, r203831

MFC: r203830, r203831

Use the SUNW,{d,i}tlb-load methods for entering locked TLB entries like
OpenBSD and OpenSolaris do instead of fiddling with the MMUs ourselves.
Unlike direct access the firmware methods don't automatically use the
next free (?) TLB slot, instead the slot to be used has to be specified.
We allocate the TLB slots for the kernel top-down as OpenSolaris suggests
that the firmware will always allocate the ones for its own use bottom-up.
Besides being simpler, according to OpenBSD using the firmware methods is
required to allow booting on Sun Fire E10K with multi-systemboard domains.

git-svn-id: svn://svn.freebsd.org/base/stable/8@205922 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f