media: i2c: hi556: 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/hi556.c

@@ -839,8 +839,7 @@ static int hi556_set_stream(struct v4l2_subdev *sd, int enable)
 
 static int __maybe_unused hi556_suspend(struct device *dev)
 {
-	struct i2c_client *client = to_i2c_client(dev);
-	struct v4l2_subdev *sd = i2c_get_clientdata(client);
+	struct v4l2_subdev *sd = dev_get_drvdata(dev);
 	struct hi556 *hi556 = to_hi556(sd);
 
 	mutex_lock(&hi556->mutex);
@@ -854,8 +853,7 @@ static int __maybe_unused hi556_suspend(struct device *dev)
 
 static int __maybe_unused hi556_resume(struct device *dev)
 {
-	struct i2c_client *client = to_i2c_client(dev);
-	struct v4l2_subdev *sd = i2c_get_clientdata(client);
+	struct v4l2_subdev *sd = dev_get_drvdata(dev);
 	struct hi556 *hi556 = to_hi556(sd);
 	int ret;