drm/i915/mtl: Add PCH support

Add support for Meteorpoint(MTP) PCH used with Meteorlake.

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220818234202.451742-7-radhakrishna.sripada@intel.com