Prevent the DMC from destroying GMBUS transfers on GLK. GMBUS
lives in PG1 so DC off is all we need.

Cc: stable@vger.kernel.org
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171208213739.16388-1-ville.syrjala@linux.intel.comReviewed-by: NDhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
(cherry picked from commit 156961ae)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>