drm/i915/dmc: Use firmware v2.06 for TGL

New firmware contains minor fixes around context restore.

Reviewed-by: Swati Sharma <swati2.sharma@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227235005.18706-1-jose.souza@intel.com