[L] Change in coreboot[main]: soc/mediatek: Add common implementation 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 implementation to configure display
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Patch Set 3:

(4 comments)

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

https://review.coreboot.org/c/coreboot/+/79776/comment/4c9bcb4b_75e87af3 :
PS3, Line 27: if (!panel || panel->disp_path == DISP_PATH_NONE) {
            : 		printk(BIOS_ERR, "%s: Panel %u is not supported.\n", __func__, active_panel_id);
            : 		return NULL;
            : 	}
I think the check can also be moved to `mtk_display_init()`.

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

https://review.coreboot.org/c/coreboot/+/79776/comment/87c8d1fe_9e592d91 :
PS3, Line 15: void
Can we return the pointer `&buffer.s` or NULL on error?

https://review.coreboot.org/c/coreboot/+/79776/comment/9f2ef9e6_403e8048 :
PS3, Line 88: (
nit: No need for parentheses.

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

https://review.coreboot.org/c/coreboot/+/79776/comment/9d9d2b17_b8c0bc64 :
PS3, Line 20: struct
const