util/spd_tools: Implement a unified version of the part_id_gen tool

Currently there are two versions of gen_part_id.go, one for LP4x and one
DDR4. This change implements a unified version of this tool.

The new part_id_gen.go is almost identical to the existing
ddr4/gen_part_id.go. The new version was based on the ddr4 version and
not the lp4x version, since the ddr4 version contains extra logic to
support fixed IDs in the mem_parts_used files.

The only non-trivial change from ddr4/gen_part_id.go is to include the
full paths of SPD files in the generated Makefile.inc. E.g. instead of

  SPD_SOURCES += lp4x-spd-1.hex

the full path relative to the coreboot root directory is included:

  SPD_SOURCES += spd/lp4x/set-0/spd-1.hex

BUG=b:191776301
TEST=For each variant of brya/volteer/dedede/guybrush/zork, run
part_id_gen and verify that the generated Makefile.inc and
dram_id.generated.txt are identical to those currently in the src tree,
except for the modified SPD file paths in Makefile.inc.
Example:
util/spd_tools/bin/part_id_gen \
  spd/lp4x/set-0 \
  src/mainboard/google/brya/variants/kano/memory \
  src/mainboard/google/brya/variants/kano/memory/mem_parts_used.txt

Change-Id: Ib33d09076f340f688519dae7956a2b27af090c0b
Signed-off-by: Reka Norman <rekanorman@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57585
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

util/spd_tools/Makefile

@@ -1,10 +1,14 @@
 SPD_GEN = bin/spd_gen
+PART_ID_GEN = bin/part_id_gen
 
-all: $(SPD_GEN)
+all: $(SPD_GEN) $(PART_ID_GEN)
 
 $(SPD_GEN):
 	go build -o $(SPD_GEN) src/spd_gen/*.go
 
+$(PART_ID_GEN):
+	go build -o $(PART_ID_GEN) src/part_id_gen/*.go
+
 clean:
 	rm -rf bin/