drm/i915: Allow cdclk squasher to be reconfigured live

Supposedly we should be able to change the cdclk squasher waveform
even when many pipes are active. Make it so.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211119131348.725220-6-mika.kahola@intel.com