drm/bridge: cdns-mhdp: fail if fast LT is used

Print an error and fail if fast LT is used. This should not happen as
fast LT is not supported, but it's better to fail than silently proceed.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/bridge/cdns-mhdp.c

@@ -818,7 +818,8 @@ static int cdns_mhdp_link_up(struct cdns_mhdp_device *mhdp)
 
 	if (mhdp->host.fast_link & mhdp->sink.fast_link) {
 		/* FIXME: implement fastlink */
-		dev_dbg(mhdp->dev, "fastlink\n");
+		dev_err(mhdp->dev, "fastlink not supported\n");
+		return -ENOTSUPP;
 	} else {
 		const u32 interval = reg0[DP_TRAINING_AUX_RD_INTERVAL] &
 				     DP_TRAINING_AUX_RD_MASK;