of: WARN on deprecated #address-cells/#size-cells handling

of: WARN on deprecated #address-cells/#size-cells handling

While OpenFirmware originally allowed walking parent nodes and default
root values for #address-cells and #size-cells, FDT has long required
explicit values. It's been a warning in dtc for the root node since the
beginning (2005) and for any parent node since 2007. Of course, not all
FDT uses dtc, but that should be the majority by far. The various
extracted OF devicetrees I have dating back to the 1990s (various
PowerMac, OLPC, PASemi Nemo) all have explicit root node properties. The
warning is disabled for Sparc as there are known systems relying on
default root node values.

Link: https://lore.kernel.org/r/20241106171028.3830266-1-robh@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>