[M] Change in coreboot[main]: mb/google/rex: Create kanix variant

[Subrata Banik (Code Review)]

Attention is currently required from: Dinesh Gehlot, Eran Mitrani, Kapil Porwal, Tarun, Tyler Wang.

Subrata Banik has posted comments on this change by Tyler Wang. ( https://review.coreboot.org/c/coreboot/+/84432?usp=email )

The change is no longer submittable: All-Comments-Resolved is unsatisfied now.

Change subject: mb/google/rex: Create kanix variant
......................................................................

Patch Set 3:

(1 comment)

File src/mainboard/google/rex/Kconfig:

https://review.coreboot.org/c/coreboot/+/84432/comment/1fcffc3a_cfce2fd2?usp... :
PS3, Line 72: 	select BOARD_GOOGLE_BASEBOARD_REX
wondering, why don't we select as part of this CL ?

```
    select SOC_INTEL_CSE_LITE_SKU
    select SOC_INTEL_CSE_PRE_CPU_RESET_TELEMETRY_V2
    select SOC_INTEL_CSE_SEND_EOP_ASYNC
```