i2c: always enable RuntimePM for the adapter device

The adapter device is a logical device. Because of that, it already uses
pm_runtime_no_callbacks() in the core. To ensure proper propagation from
the children (i2c devices) to the parent of the adapter (the HW device),
make sure RuntimePM is enabled in any case.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core.c

@@ -1564,6 +1564,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
 	dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);
 
 	pm_runtime_no_callbacks(&adap->dev);
+	pm_runtime_enable(&adap->dev);
 
 #ifdef CONFIG_I2C_COMPAT
 	res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev,
@@ -1818,6 +1819,8 @@ void i2c_del_adapter(struct i2c_adapter *adap)
 	/* device name is gone after device_unregister */
 	dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name);
 
+	pm_runtime_disable(&adap->dev);
+
 	/* wait until all references to the device are gone
 	 *
 	 * FIXME: This is old code and should ideally be replaced by an