drm: bridge/dw_hdmi: add function dw_hdmi_phy_enable_spare

RK3288 HDMI will not work without the spare bit of
HDMI_PHY_CONF0 enable

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index d39dccd..3a97c84 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -713,6 +713,13 @@
 			 HDMI_PHY_CONF0_ENTMDS_MASK);
 }
 
+static void dw_hdmi_phy_enable_spare(struct dw_hdmi *hdmi, u8 enable)
+{
+	hdmi_mask_writeb(hdmi, enable, HDMI_PHY_CONF0,
+			 HDMI_PHY_CONF0_SPARECTRL_OFFSET,
+			 HDMI_PHY_CONF0_SPARECTRL_MASK);
+}
+
 static void dw_hdmi_phy_gen2_pddq(struct dw_hdmi *hdmi, u8 enable)
 {
 	hdmi_mask_writeb(hdmi, enable, HDMI_PHY_CONF0,