[M] Change in coreboot[main]: cpu/x86/smm: Save and restore UART 8250 state on all platforms

[Martin L Roth (Code Review)]

Attention is currently required from: Arthur Heymans, Benjamin Doron, Christian Walter, Johnny Lin, Jonathan Zhang, Tim Chu.

Martin L Roth has posted comments on this change by Benjamin Doron. ( https://review.coreboot.org/c/coreboot/+/73746?usp=email )

Change subject: cpu/x86/smm: Save and restore UART 8250 state on all platforms
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Patch Set 2:

(1 comment)

Patchset:

PS2: 
This seems like a good plan if we're going to re-initialize the UART. The other option would be to just use whatever it's been set to, assuming that the remote terminal is set to the new settings and that updating the UART will mess up what's being received.

Maybe set up a Kconfig for whether to re-init in SMM?

Obviously this needs to be rebased as well.