[XS] Change in coreboot[main]: commonlib/dt: Fix incorrect cell properties

[Julius Werner (Code Review)]

Attention is currently required from: Kapil Porwal, Subrata Banik.

Julius Werner has posted comments on this change by Kapil Porwal. ( https://review.coreboot.org/c/coreboot/+/86030?usp=email )

Change subject: commonlib/dt: Fix incorrect cell properties
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Patch Set 1:

(1 comment)

Patchset:

PS1:
> If we exit from PASS#2 without returning cell properties of current parent (i.e. "/abc") the cell properties would contain values from PASS#1 which is not correct.

No, that is correct, that's the whole point of the original patch. See the FDT specification here: https://devicetree-specification.readthedocs.io/en/stable/devicetree-basics....
> The #address-cells property defines the number of <u32> cells used to encode the address field in a child node’s reg property.

The cells properties of a node define the rules for the reg properties of its _children_. That means when you use the normal pattern of
```
struct device_tree_node *node = dt_find_node(tree->root, "/cpus/cpu@0",
                                             &address_cells, &size_cells, 0);
dt_read_reg_prop(node, address_cells, size_cells, regions, ARRAY_SIZE(regions));
```
you want `address_cells` and `size_cells` to contain the value up to `/cpus`, _not_ up to `/cpus/cpu@0`. `fdt_find_node()` was already doing the same thing for the same reason.