Change in libgfxinit[master]: gma bxt: Implement CDClk switching

[Nico Huber (Code Review)]

Hello Arthur Heymans, Matt DeVillier, Thomas Heijligen,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/libgfxinit/+/35718

to look at the new patch set (#3).

Change subject: gma bxt: Implement CDClk switching
......................................................................

gma bxt: Implement CDClk switching

Again, very similar procedure to the previous generations. The
CDClk is limited to 624MHz (no fuses). Dot clocks can run at the
full CDClk speed.

If all pipes are disabled, we set CDClk to its reference rate.
In this state, the display engine is not operational and neither
are the DP Aux ports. So we have to implement Enable_CDClk() to
allow display probing without any pipe enabled.

Change-Id: I7bccbce0625a9893e2dd5c06fd1475a44987989d
Signed-off-by: Nico Huber 
---
M common/broxton/hw-gfx-gma-power_and_clocks.adb
M common/broxton/hw-gfx-gma-power_and_clocks.ads
2 files changed, 62 insertions(+), 7 deletions(-)

git pull ssh://review.coreboot.org:29418/libgfxinit refs/changes/18/35718/3