lib: utils: Add fdt_fixup_node() helper function

Add a helper function fdt_fixup_node() based on the compatible string.
This will avoid code duplication for every new node fixup being added.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>