media: i2c: ad5820: simplify getting state container

The pointer to 'struct v4l2_subdev' is stored in drvdata via
v4l2_i2c_subdev_init() so there is no point of a dance like:

    struct i2c_client *client = to_i2c_client(struct device *dev)
    struct v4l2_subdev *sd = i2c_get_clientdata(client);

This allows to remove local variable 'client' and few pointer
dereferences.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/i2c/ad5820.c

@@ -270,8 +270,7 @@ static const struct v4l2_subdev_internal_ops ad5820_internal_ops = {
  */
 static int __maybe_unused ad5820_suspend(struct device *dev)
 {
-	struct i2c_client *client = container_of(dev, struct i2c_client, dev);
-	struct v4l2_subdev *subdev = i2c_get_clientdata(client);
+	struct v4l2_subdev *subdev = dev_get_drvdata(dev);
 	struct ad5820_device *coil = to_ad5820_device(subdev);
 
 	if (!coil->power_count)
@@ -282,8 +281,7 @@ static int __maybe_unused ad5820_suspend(struct device *dev)
 
 static int __maybe_unused ad5820_resume(struct device *dev)
 {
-	struct i2c_client *client = container_of(dev, struct i2c_client, dev);
-	struct v4l2_subdev *subdev = i2c_get_clientdata(client);
+	struct v4l2_subdev *subdev = dev_get_drvdata(dev);
 	struct ad5820_device *coil = to_ad5820_device(subdev);
 
 	if (!coil->power_count)