always relocate fdt into an lmb-allocated memory block

The device tree (fdt) must always exist in within the bootmap (usually the
first 16MB of RAM).  If it doesn't, then boot_relocate_fdt() will allocate
an LMB region in the bootmap and copy the fdt into that region.  It will
also increase the size of the fdt.

If the fdt is already in the bootmap, then previously the memory was just
reserved.  There was no contingency if the reservation failed, however.

By always allocating an lmb region and copying/resizing the fdt into that
region, the code is simplified and the memory region is always allocated
properly.

Also change the types of some variables to avoid some typecasts.

Signed-off-by: Timur Tabi <timur@freescale.com>
Tested-by: Ira Snyder <iws@ovro.caltech.edu>
Acked-by: Gerald Van Baren <vanbaren@cideas.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>