drm/i915/gvt: Fix build failure after intel_engine_cs change

Change GVT-g code reference for intel_engine_cs from static array to
allocated pointer after commit 3b3f1650b1 ("drm/i915: Allocate
intel_engine_cs structure only for the enabled engines").

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161018014007.29369-1-zhenyuw@linux.intel.com

drivers/gpu/drm/i915/gvt/handlers.c

@@ -134,7 +134,7 @@ static int render_mmio_to_ring_id(struct intel_gvt *gvt, unsigned int reg)
 
 	reg &= ~GENMASK(11, 0);
 	for (i = 0; i < I915_NUM_ENGINES; i++) {
-		if (gvt->dev_priv->engine[i].mmio_base == reg)
+		if (gvt->dev_priv->engine[i]->mmio_base == reg)
 			return i;
 	}
 	return -1;