drm/i915: Cache current cdclk frequency in dev_priv
drm/i915: Cache current cdclk frequency in dev_priv

Rather that extracting the current cdclk freuqncy every time someone
wants to know it, cache the current value and use that. VLV/CHV already
stored a cached value there so just expand that to cover all platforms.

v2: Rebased to the latest
v3: Rebased to the latest
v4: Rebased to the latest
v5: Removed spurious call to 'intel_update_cdclk(dev)' based on
    Damien Lespiau's comment

Signed-off-by: Ville Syrjälä <cd6e8d405ca90be3a03d5427c5b24fbd2d68dcc4@linux.intel.com>
Signed-off-by: Mika Kahola <37fffaeeafa52a2e0cb802ff3a2d512d52ac25a1@intel.com>
Reviewed-by: Damien Lespiau <64bd3cb94f359c1a3ce68dae5e26b40578526277@intel.com>
Signed-off-by: Jani Nikula <ba783f3beccaedfda693f41a15407d612a629408@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs