util/mb/google: Add spd_tools to generate SPDs for TGL boards

This change adds tools for generating SPD files for LPDDR4x memory
used in memory down configurations on Intel Tiger Lake(TGL) based
Chrome OS platforms. These tools generate SPDs following JESD209-4C
specification and Intel recommendations(doc #616599) for LPDDR4x SPD.

Two tools are provided:
* gen_spd.go: Generates de-duplicated SPD files using a global memory
  part list provided by the mainboard in JSON format. Additionally,
  generates a SPD manifest file(in CSV format) with information about
  what memory part from the global list uses which of the generated
  SPD files.

* gen_part_id.go: Allocates DRAM strap IDs for different LPDDR4x
  memory parts used by the board. Takes as input list of memory parts
  used by the board (with one memory part on each line) and the SPD
  manifest file generated by gen_spd.go. Generates Makefile.inc for
  integrating the generated SPD files in the coreboot build.

BUG=b:155239397,b:147321551

Change-Id: Ia9b64d1d48371ccea1c01630a33a245d90f45214
Signed-off-by: Furquan Shaikh <furquan@google.com>
---
A util/mainboard/google/spd_tools/lp4x/README.md
A util/mainboard/google/spd_tools/lp4x/gen_part_id.go
A util/mainboard/google/spd_tools/lp4x/gen_spd.go
3 files changed, 1,247 insertions(+), 0 deletions(-)