[Intel-gfx] limiting modes on 4k monitors on Haswell ULT

[Dave Airlie]

Hey guys,

so I have a haswell ULT laptop (lenovo t440s), and got access to a
Samsung single panel 4k monitor (no MST).

Now we detect the monitor fine, but unfortunately the ULT hsw can't
run it over DP, as it has clock limits in place. However we still
offer the 60hz mode and we pick it by default, ensuing black screens.

I've tested the same monitor with a haswell in a t540p and it works
fine due to having the higher limits in place.

Dave.