$FreeBSD$

Patch comments:

sim/ppc/emul_chirp.c:
Add a mapping for the kernel to obtain the mapping for the
OpenFirmware callback.

sim/ppc/hw_cpu.c:
Add the device type and timebase-frequency to the cpu device.
Add code to create an instance of the cpu for the translation of the
OpenFirmware callback.

sim/ppc/hw_init.c:
Allow the simulator to load a dynamically linked OEA environment.