[Intel-gfx] Refreshed patches for encoder/connector rework

[Zhenyu Wang]

Eric, here's refreshed patch set for splitted encoder/connector
work and multifunction SDVO device support. I've tried to make
the change gradually to make it more easy to review. Also resend
your origin first two renaming patches for the whole picture. 

I've run testing for all display output types on several platforms,
and no regression found. 

Thanks.