UPSTREAM: of/fdt: Scan the root node properties earlier

Scan the root node properties (#{size,address}-cells) earlier, so that
the dt_root_addr_cells and dt_root_size_cells variables are initialized
and can be used.

Link: https://lore.kernel.org/all/20180830190523.31474-2-robh@kernel.org/


Signed-off-by: Rob Herring <robh@kernel.org>
(cherry picked from commit 554b6623)

Bug: 399581144
Change-Id: Idcd55f5a7fb87d7893ef540ed46e02f06929c9c9
Signed-off-by: Grzegorz Jaszczyk <jaszczyk@google.com>