drm/i915: Initialize dev_priv->atomic_cdclk_freq at init time

Looks like we're only initializing dev_priv->atomic_cdclk_freq
at resume and commit times, not at init time. Let's do that as
well.

We're now hitting the 'WARN_ON(intel_state->cdclk == 0)' in
hsw_compute_linetime_wm() on account of populating
intel_state->cdclk from dev_priv->atomic_cdclk_freq.
Previously we were mispopulating intel_state->cdclk with
dev_priv->cdclk_freq which always had a proper value at init
time and hence the WARN_ON() didn't trigger.

Cc: <stable@vger.kernel.org> # 4.6+: 14676ec6b1 drm/i915: Fix cdclk vs. dev_cdclk mess when not recomputing things
Cc: <stable@vger.kernel.org> # 4.6+
Cc: Matthew Auld <matthew.auld@intel.com>
Reported-by: Matthew Auld <matthew.auld@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98902
Fixes: 14676ec6b1 ("drm/i915: Fix cdclk vs. dev_cdclk mess when not recomputing things")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480428837-4207-1-git-send-email-ville.syrjala@linux.intel.com
Tested-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
(cherry picked from commit 6a259b1f8a)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -16486,6 +16486,7 @@ int intel_modeset_init(struct drm_device *dev)
 
 	intel_update_czclk(dev_priv);
 	intel_update_cdclk(dev_priv);
+	dev_priv->atomic_cdclk_freq = dev_priv->cdclk_freq;
 
 	intel_shared_dpll_init(dev);