drm/i915/tgl: Introduce Tiger Lake PCH

Add the enum additions to TGP.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: David Weinehall <david.weinehall@intel.com>
Cc: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190711173115.28296-4-lucas.demarchi@intel.com