[L] Change in coreboot[master]: device/dram/ddr: Deduplicate enum spd_dimm_type_ddr{2,3,4}

[Nico Huber (Code Review)]

Attention is currently required from: Martin L Roth, Jakub Czapiga, Arthur Heymans, Patrick Rudolph, Elyes Haouas.

Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62181 )

Change subject: device/dram/ddr: Deduplicate enum spd_dimm_type_ddr{2,3,4}
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Patch Set 8:

(1 comment)

File src/include/device/dram/ddr4.h:

https://review.coreboot.org/c/coreboot/+/62181/comment/06ccbbd1_281b520f 
PS7, Line 29: 	SPD_DDR4_DIMM_TYPE_EXTENDED		= 0x0,
> SPD_DDR2_DIMM_TYPE_MASK is used here : src/device/dram/ddr2.c  […]

Yeah, let's postpone this. Using register values in an internal API isn't a good
design choice, but that's how things are right now.

But maybe move this entry to the other enum. So we are reminded that there is
more to it.