backlight: jornada720_bl: Introduce backlight_is_blank()

Use the backlight_is_blank() helper to simplify the code a bit.

The jornada720_bl driver distinguish between backlight off
and brightness set to 0.

Thus this driver turn off backlight only when backlight_is_blank()
returns true.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/video/backlight/jornada720_bl.c

@@ -54,7 +54,7 @@ static int jornada_bl_update_status(struct backlight_device *bd)
 	jornada_ssp_start();
 
 	/* If backlight is off then really turn it off */
-	if ((bd->props.power != FB_BLANK_UNBLANK) || (bd->props.fb_blank != FB_BLANK_UNBLANK)) {
+	if (backlight_is_blank(bd)) {
 		ret = jornada_ssp_byte(BRIGHTNESSOFF);
 		if (ret != TXDUMMY) {
 			dev_info(&bd->dev, "brightness off timeout\n");