drm/i915/tgl: Add power well to support 4th pipe

Add power well 5 to support 4th pipe and transcoder on TGL.

Cc: James Ausmus <james.ausmus@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Mika Kahola <mika.kahola@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/20190711173115.28296-10-lucas.demarchi@intel.com