i2c: Constify i2c_get_clientdata's parameter

i2c_get_clientdata doesn't change the i2c_client it is passed as a
parameter, so it can be constified. Same for i2c_get_adapdata.

Signed-off-by: Jean Delvare <[e-mail]>

Documentation/i2c/writing-clients

···
 	void i2c_set_clientdata(struct i2c_client *client, void *data);
 
 	/* retrieve the value */
-	void *i2c_get_clientdata(struct i2c_client *client);
+	void *i2c_get_clientdata(const struct i2c_client *client);
 
 An example structure is below.
 

include/linux/device.h

···
 }
 #endif
 
-static inline void *dev_get_drvdata(struct device *dev)
+static inline void *dev_get_drvdata(const struct device *dev)
 {
 	return dev->driver_data;
 }

include/linux/i2c.h

···
 	return to_i2c_client(dev);
 }
 
-static inline void *i2c_get_clientdata (struct i2c_client *dev)
+static inline void *i2c_get_clientdata(const struct i2c_client *dev)
 {
 	return dev_get_drvdata (&dev->dev);
 }
···
 };
 #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
 
-static inline void *i2c_get_adapdata (struct i2c_adapter *dev)
+static inline void *i2c_get_adapdata(const struct i2c_adapter *dev)
 {
 	return dev_get_drvdata (&dev->dev);
 }