backlight: lm3630a: Fix return code of .update_status() callback

According to <linux/backlight.h> .update_status() is supposed to
return 0 on success and a negative error code otherwise. Adapt
lm3630a_bank_a_update_status() and lm3630a_bank_b_update_status() to
actually do it.

While touching that also add the error code to the failure message.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/video/backlight/lm3630a_bl.c

@@ -190,7 +190,7 @@ static int lm3630a_bank_a_update_status(struct backlight_device *bl)
 	if ((pwm_ctrl & LM3630A_PWM_BANK_A) != 0) {
 		lm3630a_pwm_ctrl(pchip, bl->props.brightness,
 				 bl->props.max_brightness);
-		return bl->props.brightness;
+		return 0;
 	}
 
 	/* disable sleep */
@@ -210,8 +210,8 @@ static int lm3630a_bank_a_update_status(struct backlight_device *bl)
 	return 0;
 
 out_i2c_err:
-	dev_err(pchip->dev, "i2c failed to access\n");
-	return bl->props.brightness;
+	dev_err(pchip->dev, "i2c failed to access (%pe)\n", ERR_PTR(ret));
+	return ret;
 }
 
 static int lm3630a_bank_a_get_brightness(struct backlight_device *bl)
@@ -267,7 +267,7 @@ static int lm3630a_bank_b_update_status(struct backlight_device *bl)
 	if ((pwm_ctrl & LM3630A_PWM_BANK_B) != 0) {
 		lm3630a_pwm_ctrl(pchip, bl->props.brightness,
 				 bl->props.max_brightness);
-		return bl->props.brightness;
+		return 0;
 	}
 
 	/* disable sleep */
@@ -287,8 +287,8 @@ static int lm3630a_bank_b_update_status(struct backlight_device *bl)
 	return 0;
 
 out_i2c_err:
-	dev_err(pchip->dev, "i2c failed to access REG_CTRL\n");
-	return bl->props.brightness;
+	dev_err(pchip->dev, "i2c failed to access (%pe)\n", ERR_PTR(ret));
+	return ret;
 }
 
 static int lm3630a_bank_b_get_brightness(struct backlight_device *bl)