drm/i915: Make cdclk part of the atomic state.

The skylake scalers depend on the cdclk freq, but that frequency can
change during a modeset. So when a modeset happens calculate the new
cdclk in the atomic state. With the transitional helpers gone the
cached value can be used in the scaler, and committed after all
crtc's are disabled.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90874
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Tested-by(IVB): Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_drv.h

@@ -244,6 +244,7 @@ typedef struct dpll {
 struct intel_atomic_state {
 	struct drm_atomic_state base;
 
+	unsigned int cdclk;
 	bool dpll_set;
 	struct intel_shared_dpll_config shared_dpll[I915_NUM_PLLS];
 };