drm/i915/tgl: Add and use new DC5 and DC6 residency counter registers

Tiger Lake has a new register offset for DC5 and DC6 residency counters.

v2:
  - Rename registers since they are not in the CSR memory range
    (requested by Anshuman)
  - Fix type (requested by Matthew)

Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190726002412.5827-2-lucas.demarchi@intel.com