drm/i915: Fix cdclk vs. dev_cdclk mess when not recomputing things

When we end up not recomputing the cdclk, we need to populate
intel_state->cdclk with the "atomic_cdclk_freq" instead of the
current cdclk_freq. When no pipes are active, the actual cdclk_freq
may be lower than what the configuration of the planes and
pipes would require from the point of view of the software state.

This fixes bogus WARNS from skl_max_scale() which is trying to check
the plane software state against the cdclk frequency. So any time
it got called during DPMS off for instance, we might have tripped
the warn if the current mode would have required a higher than
minimum cdclk.

v2: Drop the dev_cdclk stuff (Maarten)

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: bruno.pagani@ens-lyon.org
Cc: Daniel J Blueman <daniel.blueman@gmail.com>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: Joseph Yasi <joe.yasi@gmail.com>
Tested-by: Paul Bolle <pebolle@tiscali.nl>
Tested-by: Joseph Yasi <joe.yasi@gmail.com> (v1)
Cc: stable@vger.kernel.org
Fixes: 1a617b77 ("drm/i915: Keep track of the cdclk as if all crtc's were active.")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98214


Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479141311-11904-2-git-send-email-ville.syrjala@linux.intel.com