of/fdt: remove some unneeded includes

Whatever needed powerpc machdep.h appears to have been removed, so the
include can be dropped.

module.h is not needed as this code is always built-in.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Grant Likely <grant.likely@linaro.org>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Tested-by: Grant Likely <grant.likely@linaro.org>
Tested-by: Stephen Chivers <schivers@csc.com>