Change in coreboot[master]: WIP]: SPI, DMI changes to support extended BIOS region

[Srinidhi N Kaushik (Code Review)]

Srinidhi N Kaushik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/47907 )

Change subject: WIP]: SPI, DMI changes to support extended BIOS region
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Patch Set 7:

@Furquan, Added the initial changes, this is just a place holder CL. If you check it once I can update the relation chain. I didnt want to mess up the chain hence pushed it as WIP here.
I had some questions on couple of things,
1. During GPMR programming in dmi.c I think I am missing the check PCR base address being configured.
2. The MTRR programming can be better in terms of reusing the same code block. 
Also I will split this into 3 CLs as per the document.