video: tegra-dc: add panel_set_backlight call

Tegra DC driver does not call panel_set_backlight, which can
result in absence of backlight on device. Fix this by calling
panel_set_backlight with BACKLIGHT_DEFAULT just after
panel_enable_backlight.

Tested-by: Robert Eckelmann <longnoserob@gmail.com> # ASUS TF101 T20
Tested-by: Nicolas Chauvet <kwizart@gmail.com> # Paz00
Tested-by: Andreas Westman Dorcsak <hedmoo@yahoo.com> # ASUS TF T30
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # LG P895 T30
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>

drivers/video/tegra20/tegra-dc.c

@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <backlight.h>
 #include <dm.h>
 #include <fdtdec.h>
 #include <log.h>
@@ -345,6 +346,12 @@ static int tegra_lcd_probe(struct udevice *dev)
 		return ret;
 	}
 
+	ret = panel_set_backlight(priv->panel, BACKLIGHT_DEFAULT);
+	if (ret) {
+		debug("%s: Cannot set backlight to default, ret=%d\n", __func__, ret);
+		return ret;
+	}
+
 	mmu_set_region_dcache_behaviour(priv->frame_buffer, plat->size,
 					DCACHE_WRITETHROUGH);