drm/i915/skl: Don't try to read out the PCH transcoder state if not present

When the platform doesn't have a FDI link, don't try to read out the
state of a potential PCH transcoder.
Reviewed-by: Thomas Wood <thomas.wood@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
[danvet: Don't open-code HAS_FDI if there's only one place that needs
it. Acked by Damien on irc.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -7867,7 +7867,8 @@ static void haswell_get_ddi_port_state(struct intel_crtc *crtc,
 	 * DDI E. So just check whether this pipe is wired to DDI E and whether
 	 * the PCH transcoder is on.
 	 */
-	if ((port == PORT_E) && I915_READ(LPT_TRANSCONF) & TRANS_ENABLE) {
+	if (INTEL_INFO(dev)->gen < 9 &&
+	    (port == PORT_E) && I915_READ(LPT_TRANSCONF) & TRANS_ENABLE) {
 		pipe_config->has_pch_encoder = true;
 
 		tmp = I915_READ(FDI_RX_CTL(PIPE_A));