drm/i915/mtl: Don't mask off CCS according to DSS fusing

Unlike the Xe_HP platforms, MTL only has a single CCS engine; the
quad-based engine masking logic does not apply to this platform (or
presumably any future platforms that only have 0 or 1 CCS).

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220818234202.451742-5-radhakrishna.sripada@intel.com