drm/i915/gvt: not to touch undefined MOCS registers

Some engines are not available for all Gens. eg, Gen11 introduced
VCS3/VCS4/VECS2, and VCS2 is not supported on some Gen9 machines. So need to
add check before access them.
Signed-off-by: Xinyun Liu <xinyun.liu@intel.com>
Signed-off-by: Yakui Zhao <Yakui.Zhao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

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

@@ -171,6 +171,8 @@ static void load_render_mocs(struct drm_i915_private *dev_priv)
 	int ring_id, i;
 
 	for (ring_id = 0; ring_id < ARRAY_SIZE(regs); ring_id++) {
+		if (!HAS_ENGINE(dev_priv, ring_id))
+			continue;
 		offset.reg = regs[ring_id];
 		for (i = 0; i < GEN9_MOCS_SIZE; i++) {
 			gen9_render_mocs.control_table[ring_id][i] =