drm: Update generic, ttm and radeon code to Linux 4.9

* Generally cleanup non driver-specific code and increase its
robustness

* DisplayPort support improvements

* Atomic modesetting improvement

drm: Update generic, ttm and radeon code to Linux 4.9

* Generally cleanup non driver-specific code and increase its
robustness

* DisplayPort support improvements

* Atomic modesetting improvements

* Radeon performance and stability improvements

* drm/i915 stays based on Linux 4.7.10 with Linux 4.19 changes
for now

Reviewed-by: Romick

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