Change in coreboot[master]: mb/google/dedede/var/magolor: Set core display clock to 172.8 MHz

[Ren Kuo (Code Review)]

Attention is currently required from: Henry Sun, Paul Menzel, Angel Pons, Simon Yang, Kane Chen, Karthik Ramasubramanian.
Ren Kuo has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/60301 )

Change subject: mb/google/dedede/var/magolor: Set core display clock to 172.8 MHz
......................................................................

Patch Set 9:

(2 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/60301/comment/a0aa2614_2a1f96a2 
PS6, Line 9: With the default core display clock of 172.8 MHz,it improved the
           : stability of start up in Chrome OS in secure mode.
           : The rare fail system will not hang up in Chrome OS from secure mode.
           : The core display clock =  172.8 MHz in coreboot is form Intel's
           : recommendation.
> Hmmm, this paragraph is a bit confusing to understand. If I understand it correctly: […]

Yes. Your understanding is correct,and I had updated the mesage.
It' more clear.

https://review.coreboot.org/c/coreboot/+/60301/comment/6c2b0d91_a74ccdbc 
PS6, Line 18:      Check the DUTs can boot up in secure mode.
> Out of curiosity, can the CdClk frequency be increased back to regular speeds when OS GFX drivers ta […]

I'm not similar on Intel Grapic driver. I'm not sure it can be take over by it. From the fail kernel message, the clock error should be the problem. It's also 
related to the timing in OS kernel initial process.