drm/i915: Do not set L3-LLC Coherency bit in ctx descriptor

According to Spec this is a reserved bit for Gen9+ and should not be set.

Change-Id: I0215fb7057b94139b7a2f90ecc7a0201c0c93ad4
Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_lrc.c

@@ -265,6 +265,7 @@ static uint64_t execlists_ctx_descriptor(struct intel_engine_cs *ring,
 
 	desc = GEN8_CTX_VALID;
 	desc |= LEGACY_CONTEXT << GEN8_CTX_MODE_SHIFT;
+	if (IS_GEN8(ctx_obj->base.dev))
 		desc |= GEN8_CTX_L3LLC_COHERENT;
 	desc |= GEN8_CTX_PRIVILEGE;
 	desc |= lrca;