Change in coreboot[master]: util/spd_tools: Add support for exclusive IDs

[Karthik Ramasubramanian (Code Review)]

Attention is currently required from: Robert Zieba, Raul Rangel, Reka Norman, Nick Vaccaro.
Karthik Ramasubramanian has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62905 )

Change subject: util/spd_tools: Add support for exclusive IDs
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Patch Set 6:

(2 comments)

File util/spd_tools/src/part_id_gen/part_id_gen.go:

https://review.coreboot.org/c/coreboot/+/62905/comment/eebf7e9c_080fc333 
PS5, Line 332: &&
From consistency standpoint, can we add Exclusive entries to SPDToIndexMap. You can update the condition as follows:

if SPDToIndexMap[SPDFileName] < 0 || p.mapping != Exclusive {
       SPDToIndexMap[SPDFileName] = p.index
}

The or condition allows Fixed entries to overwrite the Exclusive entries in that map.

https://review.coreboot.org/c/coreboot/+/62905/comment/db76027c_391689c1 
PS5, Line 359: if index < len(assignedMapping) {
             : 				mapping = assignedMapping[index]
             : 			}
This check can be removed if you append assignedMapping after line 385:
```
    		partIdList = append(partIdList, partIds{})			 
                        assignedMapping = append(assignedMapping, Auto)

```

Then you can combine the remaining if blocks into one.