macintosh/via-pmu: Add support for m68k PowerBooks

Put #ifdefs around the Open Firmware, xmon, interrupt dispatch,
battery and suspend code. Add the necessary interrupt handling to
support m68k PowerBooks.

The pmu_kind value is available to userspace using the
PMU_IOC_GET_MODEL ioctl. It is not clear yet what hardware classes
are be needed to describe m68k PowerBook models, so pmu_kind is given
the provisional value PMU_UNKNOWN.

To find out about the hardware, user programs can use /proc/bootinfo
or /proc/hardware, or send the PMU_GET_VERSION command using /dev/adb.

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>