- Prepare mk48txxvar.h and leave only register definitions in mk48txxreg.h.
- Define struct mk48txx_softc as usual devices and allocate necessary
members like struct todr_chip_handle in it.
- Change mk48txx_attach(), mk48txx_nvwr() and mk48txx_nvrd() to take
struct mk48txx_softc.
locations. If passed NULL, the old behaviour using bus_space_{read,write}_1()
is used. Otherwise, all access to the chip goes via the MD functions.
This is necessary for mvmeppc boards where the mk48txx NVRAM/RTC is not
directly addressable.
