drm/sti: fix opencoded use of drm_panel_*

Use the drm_panel_(enable|disable|get_modes) functions.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190804201637.1240-9-sam@ravnborg.org

drivers/gpu/drm/sti/sti_dvo.c

@@ -221,8 +221,7 @@ static void sti_dvo_disable(struct drm_bridge *bridge)
 
 	writel(0x00000000, dvo->regs + DVO_DOF_CFG);
 
-	if (dvo->panel)
-		dvo->panel->funcs->disable(dvo->panel);
+	drm_panel_disable(dvo->panel);
 
 	/* Disable/unprepare dvo clock */
 	clk_disable_unprepare(dvo->clk_pix);
@@ -262,8 +261,7 @@ static void sti_dvo_pre_enable(struct drm_bridge *bridge)
 	if (clk_prepare_enable(dvo->clk))
 		DRM_ERROR("Failed to prepare/enable dvo clk\n");
 
-	if (dvo->panel)
-		dvo->panel->funcs->enable(dvo->panel);
+	drm_panel_enable(dvo->panel);
 
 	/* Set LUT */
 	writel(config->lowbyte,  dvo->regs + DVO_LUT_PROG_LOW);
@@ -340,7 +338,7 @@ static int sti_dvo_connector_get_modes(struct drm_connector *connector)
 	struct sti_dvo *dvo = dvo_connector->dvo;
 
 	if (dvo->panel)
-		return dvo->panel->funcs->get_modes(dvo->panel);
+		return drm_panel_get_modes(dvo->panel);
 
 	return 0;
 }