[Intel-gfx] Fixes that failed cherry-pick to 5.10

[Chris Wilson]

Quoting Rodrigo Vivi (2020-10-19 18:53:10)
> Hi Chris and Ville,
> 
> Failed to cherry-pick:
> 233c1ae3c83f ("drm/i915/gt: Wait for CSB entries on Tigerlake")

See https://cgit.freedesktop.org/~ickle/linux-2.6/log/?h=dif for the
dependencies.
-Chris