media: atomisp: fix the uninitialized use and rename "retvalue"

Inside function mt9m114_detect(), variable "retvalue" could
be uninitialized if mt9m114_read_reg() returns error, however, it
is used in the later if statement, which is potentially unsafe.

The local variable "retvalue" is renamed to "model" to avoid
confusion.

Link: https://lore.kernel.org/linux-media/20210625053858.3862-1-yzhai003@ucr.edu
Fixes: ad85094b ("Revert "media: staging: atomisp: Remove driver"")
Signed-off-by: Yizhuo <yzhai003@ucr.edu>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/atomisp/i2c/atomisp-mt9m114.c

@@ -1545,16 +1545,19 @@ static struct v4l2_ctrl_config mt9m114_controls[] = {
 static int mt9m114_detect(struct mt9m114_device *dev, struct i2c_client *client)
 {
 	struct i2c_adapter *adapter = client->adapter;
-	u32 retvalue;
+	u32 model;
+	int ret;
 
 	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C)) {
 		dev_err(&client->dev, "%s: i2c error", __func__);
 		return -ENODEV;
 	}
-	mt9m114_read_reg(client, MISENSOR_16BIT, (u32)MT9M114_PID, &retvalue);
-	dev->real_model_id = retvalue;
+	ret = mt9m114_read_reg(client, MISENSOR_16BIT, MT9M114_PID, &model);
+	if (ret)
+		return ret;
+	dev->real_model_id = model;
 
-	if (retvalue != MT9M114_MOD_ID) {
+	if (model != MT9M114_MOD_ID) {
 		dev_err(&client->dev, "%s: failed: client->addr = %x\n",
 			__func__, client->addr);
 		return -ENODEV;