drm/sun4i: tcon: Move the muxing out of the mode set function

The muxing can actually happen on both channels on some SoCs, so it makes
more sense to just move it out of the sun4i_tcon1_mode_set function and
create a separate function that needs to be called by the encoders.

Let's do that and convert the existing drivers.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

drivers/gpu/drm/sun4i/sun4i_tcon.h

@@ -196,6 +196,8 @@ void sun4i_tcon_enable_vblank(struct sun4i_tcon *tcon, bool enable);
 /* Mode Related Controls */
 void sun4i_tcon_switch_interlace(struct sun4i_tcon *tcon,
 				 bool enable);
+void sun4i_tcon_set_mux(struct sun4i_tcon *tcon, int channel,
+			struct drm_encoder *encoder);
 void sun4i_tcon0_mode_set(struct sun4i_tcon *tcon,
 			  struct drm_display_mode *mode);
 void sun4i_tcon1_mode_set(struct sun4i_tcon *tcon,