MIPS: relocate: Optionally relocate the DTB

If the DTB is located in the target memory area for the relocated kernel
it needs to be relocated as well before kernel relocation takes place.

After copying the DTB use the new plat_fdt_relocated() API from the
relocated kernel to ensure the relocated kernel updates any information
that it may have cached about the location of the DTB.

plat_fdt_relocated is declared as a weak symbol so that platforms that
do not require it do not need to implement the method.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14616/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>