Change in coreboot[master]: drivers/intel/gma: Support IGD Opregion 2.1

[Furquan Shaikh (Code Review)]

Attention is currently required from: Nico Huber, Krishna Prabhakaran, Maulik V Vaghela, Selma Bensaid, Angel Pons, Subrata Banik, Meera Ravindranath, Patrick Rudolph.
Furquan Shaikh has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52758 )

Change subject: drivers/intel/gma: Support IGD Opregion 2.1
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Patch Set 14:

(1 comment)

File src/drivers/intel/gma/Kconfig:

https://review.coreboot.org/c/coreboot/+/52758/comment/5ae478b6_4b3dd252 
PS13, Line 105: INTEL_GMA_OPREGION_2_0
> Hmmm, can we try to not rely on implicit defaults? I'd rather have each platform explicitly select the Opregion version it is meant to be used with

That sounds okay to me. Ideally, I think we should deprecate support for 2.0 if all platforms can be moved forward to 2.1. For now, your suggestion makes sense.