Change in coreboot[master]: mb/google/guybrush/var/dewatt: add specific SPD hex for dewatt

[Rob Barnes (Code Review)]

Attention is currently required from: Robert Zieba, Chris Wang, Karthik Ramasubramanian, Felix Held.
Rob Barnes has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63132 )

Change subject: mb/google/guybrush/var/dewatt: add specific SPD hex for dewatt
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Patch Set 4: Code-Review-1

(1 comment)

File src/mainboard/google/guybrush/variants/dewatt/memory/Makefile.inc:

https://review.coreboot.org/c/coreboot/+/63132/comment/f4cc114f_68a941ed 
PS4, Line 16: SPD_SOURCES += $(src)/mainboard/$(MAINBOARDDIR)/variants/$(VARIANT_DIR)/memory/K4U6E3S4AB-MGCL.hex     # ID = 9(0b1001)  Parts = K4U6E3S4AB-MGCL
> Is there no way to update the memory_parts. […]

+1. As is, this will get overwritten every time part_id_gen is run. We could modify  apcb_v3_edit.py to inject the part number at this index. Alternatively, we could modify part_id_gen to support special spd binaries.