[coreboot-gerrit] Change in coreboot[master]: mb/hp/z220_series: Convert z220_sff_workstation into variant

[Angel Pons (Code Review)]

Attention is currently required from: Felix Singer, Damien Zammit, Edward O'Callaghan.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62808 )

Change subject: mb/hp/z220_series: Convert z220_sff_workstation into variant
......................................................................

Patch Set 2:

(1 comment)

File src/mainboard/hp/z220_series/Kconfig:

https://review.coreboot.org/c/coreboot/+/62808/comment/8b74b563_b3ba8c46 
PS1, Line 1: BOARD_HP_Z220_SERIES
> Done

I think the `_SERIES` suffix should be indicative enough that the symbol serves as a base for other options, but I don't think it's something to lose sleep over.