hwmon: (lm90) Unmask hardware interrupt

The ALERT interrupt is enabled by default after power-on, but it could
be masked by bootloader. For example this is the case on Acer A500 tablet
device. Unmask the hardware interrupt if interrupt is provided.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/lm90.c

@@ -1704,6 +1704,13 @@ static int lm90_init_client(struct i2c_client *client, struct lm90_data *data)
 	if (data->kind == max6696)
 		config &= ~0x08;
 
+	/*
+	 * Interrupt is enabled by default on reset, but it may be disabled
+	 * by bootloader, unmask it.
+	 */
+	if (client->irq)
+		config &= ~0x80;
+
 	config &= 0xBF;	/* run */
 	lm90_update_confreg(data, config);