drm/i915/display: Introduce HAS_CDCLK_SQUASH macro

Driver had discrepancy in how cdclk squash and crawl support
were checked. Like crawl, add squash as a 1 bit feature flag
to the display section of DG2.

Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221025223042.138810-2-anusha.srivatsa@intel.com