drm/bridge: dw-hdmi: Remove unused hdmi_enable_overflow_interrupts()

The cable_plugin member never receives an assignment, so it is always
false, which causes hdmi_enable_overflow_interrupts() to never
be called as per the logic below:

	if (hdmi->cable_plugin && hdmi->sink_is_hdmi)
		hdmi_enable_overflow_interrupts(hdmi);

This has been the case since the driver was originally introduced
in commit 9aaf880e ("imx-drm: Add mx6 hdmi transmitter support").

Remove the cable_plugin element and the hdmi_enable_overflow_interrupts()
function that is never called.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> # On R-Car H3
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1518812170-22687-1-git-send-email-festevam@gmail.com

drivers/gpu/drm/bridge/synopsys/dw-hdmi.c

@@ -147,7 +147,6 @@ struct dw_hdmi {
 	int vic;
 
 	u8 edid[HDMI_EDID_LEN];
-	bool cable_plugin;
 
 	struct {
 		const struct dw_hdmi_phy_ops *ops;
@@ -1679,12 +1678,6 @@ static void dw_hdmi_clear_overflow(struct dw_hdmi *hdmi)
 		hdmi_writeb(hdmi, val, HDMI_FC_INVIDCONF);
 }
 
-static void hdmi_enable_overflow_interrupts(struct dw_hdmi *hdmi)
-{
-	hdmi_writeb(hdmi, 0, HDMI_FC_MASK2);
-	hdmi_writeb(hdmi, 0, HDMI_IH_MUTE_FC_STAT2);
-}
-
 static void hdmi_disable_overflow_interrupts(struct dw_hdmi *hdmi)
 {
 	hdmi_writeb(hdmi, HDMI_IH_MUTE_FC_STAT2_OVERFLOW_MASK,
@@ -1774,8 +1767,6 @@ static int dw_hdmi_setup(struct dw_hdmi *hdmi, struct drm_display_mode *mode)
 	hdmi_tx_hdcp_config(hdmi);
 
 	dw_hdmi_clear_overflow(hdmi);
-	if (hdmi->cable_plugin && hdmi->sink_is_hdmi)
-		hdmi_enable_overflow_interrupts(hdmi);
 
 	return 0;
 }