km(4): Support for sensors in AMDs Kaveri and Kabini APUs

* Add support for Family 15h Models 30h-3Fh (Kaveri) and for
  Family 16h Models 00h-0Fh (Kabini).
kernel - Fix crypto boots and rescue boots

* The kernel text+data+bss is too big, the loader's 64MB heap can't fit
  it plus modules plus the initrd image any more.  Fix by reducing the
  kernel's BSS.

* Reduce the BSS allocation for CPU_prvspace[] from 11MB (45056 x 256 cpus)
  to ~45056 for the BSP and dynamically allocate the globaldata space for
  the APs.  Also saves ~11MB of ram or so on normal systems.

* Reduce the BSS allocation for cpu_map_entry_init[].  Only the BSP needs
  MAXCPU+1 pre-cached vm_map_entry structures.  The APs can make due with
  8 or so before the VM system comes up sufficiently to dynamically allocate
  these structures.  This saves around ~6.5MB of ram on normal systems.