drm/i915/glk: Add missing bits to allow runtime pm suspend on GLK.

Besides having the DMC firmware in place and loaded let's
handle runtime suspend and dc9 as we do for Broxton.

Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481902946-18593-2-git-send-email-ander.conselvan.de.oliveira@intel.com