drm: bridge: dw-hdmi: Constify mode argument to internal functions

Several internal functions take a drm_display_mode argument to configure
the HDMI encoder or the HDMI PHY. They must not modify the mode, make
the pointer const to enforce that.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200526011505.31884-18-laurent.pinchart+renesas@ideasonboard.com

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

@@ -1628,7 +1628,8 @@ static void hdmi_tx_hdcp_config(struct dw_hdmi *hdmi)
 		  HDMI_A_HDCPCFG1_ENCRYPTIONDISABLE_MASK, HDMI_A_HDCPCFG1);
 }
 
-static void hdmi_config_AVI(struct dw_hdmi *hdmi, struct drm_display_mode *mode)
+static void hdmi_config_AVI(struct dw_hdmi *hdmi,
+			    const struct drm_display_mode *mode)
 {
 	struct hdmi_avi_infoframe frame;
 	u8 val;
@@ -1756,7 +1757,7 @@ static void hdmi_config_AVI(struct dw_hdmi *hdmi, struct drm_display_mode *mode)
 }
 
 static void hdmi_config_vendor_specific_infoframe(struct dw_hdmi *hdmi,
-						 struct drm_display_mode *mode)
+						  const struct drm_display_mode *mode)
 {
 	struct hdmi_vendor_infoframe frame;
 	u8 buffer[10];
@@ -2112,7 +2113,8 @@ static void hdmi_disable_overflow_interrupts(struct dw_hdmi *hdmi)
 		    HDMI_IH_MUTE_FC_STAT2);
 }
 
-static int dw_hdmi_setup(struct dw_hdmi *hdmi, struct drm_display_mode *mode)
+static int dw_hdmi_setup(struct dw_hdmi *hdmi,
+			 const struct drm_display_mode *mode)
 {
 	int ret;