drm/i915/cdclk: Only compute squash waveform when necessary

It is no use computing the squash waveform if we are not going to use
it. Move the call to cdclk_squash_waveform() inside the block guarded by
HAS_CDCLK_SQUASH(dev_priv).

v2:
  - Move "u16 waveform" declaration to inside the block where it is
    initialized and used. (Matt)

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240312163639.172321-4-gustavo.sousa@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>