Change in coreboot[master]: lenovo/x230: introduce FHD variant

[Nico Huber (Code Review)]

Attention is currently required from: Felix Singer, Xue Yao, Paul Menzel, Kilian Neuner, Angel Pons, Charles Moyes, Alexander Couzens.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/28950 )

Change subject: lenovo/x230: introduce FHD variant
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Patch Set 22:

(5 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/28950/comment/60345aca_7e50b5dc 
PS22, Line 14: uses the same method of enabling the custom eDP panel.
If there was a single way a mod could do it or if this change
would document what mod in what configuration was tested, it
would have been merged years ago, AFAICT.

https://review.coreboot.org/c/coreboot/+/28950/comment/e1ea45b2_f107ec21 
PS22, Line 18: brightness controls to work out of the box.
This seems misleading. Yes, it "allows" things to work OOB. But it
doesn't always work OOB. The nitrocaster mod in its default confi-
guration, for instance, is designed to work without firmware modi-
fications and doesn't work well if the firmware is adapted, AIUI.

https://review.coreboot.org/c/coreboot/+/28950/comment/2bbe726e_4a0ebd7c 
PS22, Line 24: - Set the DP-3 as internally connected.
This part is missing in the libgfxinit configuration.

File src/mainboard/lenovo/x230/Kconfig:

https://review.coreboot.org/c/coreboot/+/28950/comment/adca0244_3401b880 
PS19, Line 26: 	select GFX_GMA_PANEL_1_ON_EDP if BOARD_LENOVO_X230_EDP
> Done

`_EDP` here means the dedicated eDP port. I assume this needs a `DP3`
default for `config GFX_GMA_PANEL_1_PORT`.

File src/mainboard/lenovo/x230/Kconfig.name:

https://review.coreboot.org/c/coreboot/+/28950/comment/fe1c3f04_a84348d5 
PS22, Line 11: 	bool "ThinkPad X230 eDP Mod (2K/FHD)"
Please add a help text about tested mods and their configuration.