of: Remove a duplicated code block

address.c has a same code block with fdt_address.c.

Remove a copy by moving the duplicated code block into of_private.h.

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
Link: https://lore.kernel.org/r/20250109-of_core_fix-v4-8-db8a72415b8c@quicinc.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>