Change in coreboot[master]: mb/intel/shadowmountain: Add bootblock and verstage code

[V Sowmya (Code Review)]

Attention is currently required from: Martin Roth, Tim Wawrzynczak, Sugnan Prabhu S, Angel Pons, Balaji Manigandan, Aamir Bohra.
V Sowmya has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/49479 )

Change subject: mb/intel/shadowmountain: Add bootblock and verstage code
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Patch Set 6:

(1 comment)

File src/mainboard/intel/shadowmountain/Kconfig:

https://review.coreboot.org/c/coreboot/+/49479/comment/4bbeec44_9fa1a32d 
PS5, Line 24: default y
> abuild has an option to enable building for CHROMEOS, and Jenkins tests boards with and without this […]

@Angel, I tried building for !chromeos also (https://review.coreboot.org/c/coreboot/+/49056) and i didn't see any failures but to align with this last review comment (https://review.coreboot.org/c/coreboot/+/49056/4//COMMIT_MSG#7) i removed the default and selected it under board config.