Change in coreboot[master]: soc/intel: drop unneeded ISST configuration code

[Matt DeVillier (Code Review)]

Matt DeVillier has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/46460 )

Change subject: soc/intel: drop unneeded ISST configuration code
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Patch Set 2:

IMO a cleaner approach would be to move the code to a function in the MSR common block, switch any boards disabling ISST to use the function directly vs setting DT register, and then dropping from the SoC code