drm/stm: dsi: stm mipi dsi doesn't print error on probe deferral

Change DSI driver to not print an error trace when probe
is deferred for a clock resource.
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Reviewed-by: Philippe Cornu <philippe.cornu@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1579602245-7577-1-git-send-email-yannick.fertre@st.com

drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

@@ -377,7 +377,9 @@ static int dw_mipi_dsi_stm_probe(struct platform_device *pdev)
 	dsi->pllref_clk = devm_clk_get(dev, "ref");
 	if (IS_ERR(dsi->pllref_clk)) {
 		ret = PTR_ERR(dsi->pllref_clk);
-		DRM_ERROR("Unable to get pll reference clock: %d\n", ret);
+		if (ret != -EPROBE_DEFER)
+			DRM_ERROR("Unable to get pll reference clock: %d\n",
+				  ret);
 		goto err_clk_get;
 	}