Change in coreboot[master]: soc/intel/common: Configure TCSS access through IOE P2SB

[John Zhao (Code Review)]

Attention is currently required from: Paul Menzel, Eric Lai, Angel Pons, Patrick Rudolph, EricR Lai.
John Zhao has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62723 )

Change subject: soc/intel/common: Configure TCSS access through IOE P2SB
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Patch Set 3:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/62723/comment/3ac45867_aaa1a644 
PS2, Line 9: This change abstracts the TCSS access through IOE P2SB on Meteor Lake.
> I still do not fully understand, why the common code needs to be adapted, and what changed in Meteor […]

TGL/ADL accesses TCSS through REGBAR and MTL through sideband interface(SBI) which is in the IOE die. The common code abstracts the TCSS access with ioe_p2sb_sbi_read and ioe_p2sb_sbi_write once the MTL platform code selects Kconfig _TCSS_REG_ACCESS_SBI and _IOE_P2SB, enables ioe p2sb bar and marks ioe_p2sb as hidden, etc. I put the concise statement "This change abstracts the TCSS access through IOE P2SB on Meteor Lake." here. Please advise proper phrases if that is not clear.