Input: max8997_haptic - add error handling for regulator and pwm

Let's start checking return value of regulator_enable and pwm_enable to
avoid errors. Fixes the following warning:

drivers/input/misc/max8997_haptic.c:185:19: warning: ignoring return value of ‘regulator_enable’, declared with attribute warn_unused_result [-Wunused-result]
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/max8997_haptic.c

@@ -181,11 +181,21 @@ static void max8997_haptic_enable(struct max8997_haptic *chip)
 	}
 
 	if (!chip->enabled) {
-		chip->enabled = true;
-		regulator_enable(chip->regulator);
+		error = regulator_enable(chip->regulator);
+		if (error) {
+			dev_err(chip->dev, "Failed to enable regulator\n");
+			goto out;
+		}
 		max8997_haptic_configure(chip);
-		if (chip->mode == MAX8997_EXTERNAL_MODE)
-			pwm_enable(chip->pwm);
+		if (chip->mode == MAX8997_EXTERNAL_MODE) {
+			error = pwm_enable(chip->pwm);
+			if (error) {
+				dev_err(chip->dev, "Failed to enable PWM\n");
+				regulator_disable(chip->regulator);
+				goto out;
+			}
+		}
+		chip->enabled = true;
 	}
 
 out: