Change in coreboot[master]: soc/intel/graphics: Create Kconfig for shifting graphic memory base

[Subrata Banik (Code Review)]

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

Change subject: soc/intel/graphics: Create Kconfig for shifting graphic memory base
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Patch Set 11:

(3 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/61389/comment/e87cf6a4_98a0dfc6 
PS11, Line 7: soc/intel/graphics: Create Kconfig for shifting graphic memory base
You might need to rework on commit msg else I agree with this problem statement.

Also, may be something like SOC_INTEL_GFX_GMADR_BEHIND_GTT could be your parent Kconfig which decides if we need such additional arithmetic or not.

SOC_INTEL_GFX_MEMBASE_OFFSET can be dependent on parent Kconfig

File src/soc/intel/common/block/graphics/graphics.c:

https://review.coreboot.org/c/coreboot/+/61389/comment/0c4e42e0_eec0be3b 
PS11, Line 122: 	printk(BIOS_INFO, "gfx memory bar(0x18) = 0x%lx GFX_MEMBASE_OFFSET = 0x%x\n",
              : 		memory_base, CONFIG_SOC_INTEL_GFX_MEMBASE_OFFSET);
do we need this ?

https://review.coreboot.org/c/coreboot/+/61389/comment/aeb97ec8_dadb3089 
PS11, Line 129: memory_base = memory_base + CONFIG_SOC_INTEL_GFX_MEMBASE_OFFSET;
memory_base += CONFIG_SOC_INTEL_GFX_MEMBASE_OFFSET;

Assuming CONFIG_SOC_INTEL_GFX_MEMBASE_OFFSET is `0` unless overridden by SoC?

Also, shouldn't this code sits at line above `if clause` ? Because the purpose of that if clause if to ensure memory_base is not zero.