util/spd_tools: Automatically determine the SPD dir in part_id_gen

util/spd_tools: Automatically determine the SPD dir in part_id_gen

Currently, one of the arguments to part_id_gen is the directory
containing the SPD files, e.g. spd/lp4x/set-0. This requires the user of
the tool to understand the spd/ directory structure, and manually look
up the set number corresponding to their platform.

Change part_id_gen to take the platform and memory technology as
arguments instead of the SPD directory, and automatically determine the
SPD directory by reading the platforms manifest file generated by
spd_gen.go.

BUG=b:191776301
TEST=Run part_id_gen and check that the generated Makefile.inc and
dram_id.generated.txt are the same as before. Example:
util/spd_tools/bin/part_id_gen \
  ADL \
  lp4x \
  src/mainboard/google/brya/variants/kano/memory \
  src/mainboard/google/brya/variants/kano/memory/mem_parts_used.txt

Change-Id: I7cd7243d76b5769e8a15daa56b8438274bdd8e96
Signed-off-by: Reka Norman <rekanorman@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57586
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>