drm/omap: Fix crash when using LCD3 overlay manager

The channel_names list didn't have a string populated for LCD3 manager, this
results in a crash when the display's output is connected to LCD3. Add an entry
for LCD3.

Reported-by: Somnath Mukherjee <somnath@ti.com>
Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/omap_crtc.c

@@ -654,6 +654,7 @@ static const char *channel_names[] = {
 		[OMAP_DSS_CHANNEL_LCD] = "lcd",
 		[OMAP_DSS_CHANNEL_DIGIT] = "tv",
 		[OMAP_DSS_CHANNEL_LCD2] = "lcd2",
+		[OMAP_DSS_CHANNEL_LCD3] = "lcd3",
 };
 
 void omap_crtc_pre_init(void)