drm/i915/dmc: add support to load dmc_header version 3

Main difference is that now there are up to 20 MMIOs that can be set and
a lot of noise due to the struct changing the fields in the middle.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190607091230.1489-8-lucas.demarchi@intel.com