[Intel-gfx] [PATCH] honor VBIOS SSC & TV settings

[Jesse Barnes]

I've been doing some work lately to use more of the VBIOS settings where 
possible.  This patch adds support for using the VBIOS for TV connector 
detection and SSC information.  On my T61 at least, using this patch keeps me 
from having to use the T61 TV ignore quirk.

SSC (spread spectrum clock) is a EMI reducing feature 855+ chips support.  It 
allows the OEM to provide an external reference clock and connect it to the 
GPU to modulate the display clock frequency.  Since it requires an external 
part, information about its presence and frequency is supposed to be in the 
VBIOS general info block.

I'm not sure how accurate the VBIOS info is for either TV or SSC info, so I'd 
like to get some feedback.  Can people give this a try?  It disables the TV 
quirk logic, so it'll rely on the VBIOS for getting TV output presence info.  
And it will unconditionally use SSC if it finds it, so you'll see a message 
like
(II) intel(0): using SSC reference clock of 100 MHz
in your log if it ends up getting used.

Please provide testing feedback on both features as a reply to this message.

Thanks,
Jesse