util/spd_tools: Add max ID check for auto-generated IDs to part_id_gen

Currently, the maximum part ID of 15 is enforced only for manually
assigned IDs. Also enforce it for automatically assigned IDs.

BUG=b:191776301
TEST=part_id_gen fails when the number of part IDs which would be
assigned is greater than MaxMemoryId.

Signed-off-by: Reka Norman <rekanorman@google.com>
Change-Id: I802190a13b68439ccbcdb28300ccc5fd1b38a9c9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57691
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

util/spd_tools/src/part_id_gen/part_id_gen.go

@@ -240,6 +240,9 @@ func genPartIdInfo(parts []usedPart, partToSPDMap map[string]string, SPDToIndexM
 		// Append new entry
 		if index == -1 {
 			index = len(partIdList)
+			if index > MaxMemoryId {
+				return nil, fmt.Errorf("Maximum part ID %d exceeded.", MaxMemoryId)
+			}
 			partIdList = append(partIdList, partIds{})
 		}