The flat tree unflatting path is using unsigned longs to carry around
virtual address pointers to the device tree and the allocated memory
used to unpack it. This is a little insane since every access to them
needs to be cast to a pointer type before using it. This patch changes
the data type to void* for the 'start' and 'mem' pointers and reworks
the unflattening functions to use those values directly which results in
slightly simpler code.
Signed-off-by: Grant Likely <grant.likely@linaro.org>