[M] Change in coreboot[main]: soc/mediatek: Add common implmentation to configure display

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Hung-Te Lin, Paul Menzel, Yidi Lin.

Yu-Ping Wu has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/79776?usp=email )

Change subject: soc/mediatek: Add common implmentation to configure display
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Patch Set 1:

(8 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/79776/comment/bc69738e_b29da548 :
PS1, Line 13: mtcmos_display_power_on
nit: `mtcmos_display_power_on()`

https://review.coreboot.org/c/coreboot/+/79776/comment/bbc5d2fd_545ea20e :
PS1, Line 28: soc
nit: `mediatek`

https://review.coreboot.org/c/coreboot/+/79776/comment/1f5bcdc2_6f99a6fe :
PS1, Line 29: refacts
Do you mean `refactors`?

File src/mainboard/google/geralt/panel.h:

https://review.coreboot.org/c/coreboot/+/79776/comment/9d825f48_e693c00d :
PS1, Line 23: struct panel_description *get_active_panel(void);
I think the declaration should be kept here, because the implementation is in geralt/panel.c.

File src/soc/mediatek/common/display.c:

https://review.coreboot.org/c/coreboot/+/79776/comment/5240a02b_c853c63a :
PS1, Line 13: configure_display
Consider renaming it to `mtk_display_init`?

https://review.coreboot.org/c/coreboot/+/79776/comment/3d4ed732_101c102f :
PS1, Line 42: 		if (panel->get_edid && panel->get_edid(panel) < 0)
So, this is only for eDP bridges, right? For consistency, I think `get_mipi_cmd_from_cbfs()`, which also sets `panel->s->edid`, can also be moved to soc/meditek/common/. That would also reduce duplicate code for MediaTek boards (for example corsola also has `get_panel_from_cbfs()`). Then the logic here can be

```
if (panel->get_edid) {
    panel->get_edid(panel);
} else {
    panel_serializable_data mipi_data;
    get_mipi_panel_from_cbfs(&mipi_data);
}
```

And `s` can also be removed from `panel`. What do you think?

File src/soc/mediatek/common/include/soc/ddp_common.h:

https://review.coreboot.org/c/coreboot/+/79776/comment/6cfab11e_34262aca :
PS1, Line 142: enum disp_path_sel {
I think this should be put in mediatek/common/.../display.h, and then include display.h from mt8188/.../ddp.h (not the other way around).

File src/soc/mediatek/common/include/soc/display.h:

https://review.coreboot.org/c/coreboot/+/79776/comment/694f054f_98fff66b :
PS1, Line 13: configure_panel_backlight
configure_backlight