Change in coreboot[master]: soc/intel/graphics: Add override api for graphics_get_memory_base()

[Nico Huber (Code Review)]

Attention is currently required from: Subrata Banik, Wonkyu Kim, Ethan Tsao, Ravishankar Sarawadi, Tim Wawrzynczak, Paul Menzel, Raj Astekar, Patrick Rudolph.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/61389 )

Change subject: soc/intel/graphics: Add override api for graphics_get_memory_base()
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Patch Set 8:

(1 comment)

Patchset:

PS7:
> In future platform, PCI config 0x18 still has memory bar but display memory may not same as memory bar address.

So, in case it is not at the same address, where will it be?