[S] Change in coreboot[master]: mb/google/rex: Set frequency and gears for SaGv points

[Subrata Banik (Code Review)]

Attention is currently required from: Bora Guvendik, Tarun Tuli, Kapil Porwal.

Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/75291 )

Change subject: mb/google/rex: Set frequency and gears for SaGv points
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Patch Set 3:

(1 comment)

File src/mainboard/google/rex/variants/baseboard/rex/devicetree.cb:

https://review.coreboot.org/c/coreboot/+/75291/comment/e9277c76_a7a279f3 
PS3, Line 55: 
wondering how do you derive those freqs ?

this is what I found at Intel PnP update about different SaGv endpoint freq
```
+-------+--------+
|   0   | 3200   |
|   1   | 4267   |
|   2   | 7467   |
|   3   | 4267   |
+-------+--------+
```