drm/i915/glk: Fix DMC/DC state idleness calculation

According to BSpec GLK like BXT needs to ignore the idle state of cores
before starting the DMC firmware's DC state handler.

Fixes: dbb28b5c ("drm/i915/DMC/GLK: Load DMC on GLK")
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171003095159.711-2-imre.deak@intel.com
(cherry picked from commit b7208a3f)
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/intel_csr.c

@@ -216,7 +216,7 @@ static void gen9_set_dc_state_debugmask(struct drm_i915_private *dev_priv)
 
 	mask = DC_STATE_DEBUG_MASK_MEMORY_UP;
 
-	if (IS_BROXTON(dev_priv))
+	if (IS_GEN9_LP(dev_priv))
 		mask |= DC_STATE_DEBUG_MASK_CORES;
 
 	/* The below bit doesn't need to be cleared ever afterwards */