[S] Change in coreboot[master]: soc/intel/cmn/graphics: Implement API for IGD to join the MBUS

[Paul Menzel (Code Review)]

Attention is currently required from: Subrata Banik.

Paul Menzel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/76928?usp=email )

Change subject: soc/intel/cmn/graphics: Implement API for IGD to join the MBUS
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Patch Set 2:

(4 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/76928/comment/07dec02b_debf0b1b :
PS2, Line 10: required operations before handing the controlto the payload or OS. 
Trailing space.

https://review.coreboot.org/c/coreboot/+/76928/comment/ed0cf9b6_27bb5d97 :
PS2, Line 10: controlto
control to

https://review.coreboot.org/c/coreboot/+/76928/comment/bd3d2794_45ce069b :
PS2, Line 29: When enabled, saves 75ms-80ms of the boot time by avoiding redundant
            : display initialization by kernel graphics driver (i.e., i915_gfx).
Is this happening on shipped ChromeOS devices?

https://review.coreboot.org/c/coreboot/+/76928/comment/8061e0de_bd12fe31 :
PS2, Line 31: 
It’d be great, if you added the available modes, and why hashing mode is chosen.