v4l2: camera_proxy: Fix compilation error use of undeclared identifier 'ret'

Refactoring of the camera_proxy have left the 'ret' variable undeclared,
declare it.

../../src/v4l2/v4l2_camera_proxy.cpp:273:2: error: use of undeclared identifier 'ret'
        ret = vcam_->invokeMethod(&V4L2Camera::configure,
        ^
../../src/v4l2/v4l2_camera_proxy.cpp:278:6: error: use of undeclared identifier 'ret'
        if (ret < 0)

Fixes: fce110c6d9 ("v4l2: camera_proxy: Break out try_fmt")
Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Acked-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/v4l2/v4l2_camera_proxy.cpp

@@ -270,11 +270,11 @@ int V4L2CameraProxy::vidioc_s_fmt(struct v4l2_format *arg)
 	tryFormat(arg);
 
 	Size size(arg->fmt.pix.width, arg->fmt.pix.height);
-	ret = vcam_->invokeMethod(&V4L2Camera::configure,
-				  ConnectionTypeBlocking,
-				  &streamConfig_, size,
-				  v4l2ToDrm(arg->fmt.pix.pixelformat),
-				  bufferCount_);
+	int ret = vcam_->invokeMethod(&V4L2Camera::configure,
+				      ConnectionTypeBlocking,
+				      &streamConfig_, size,
+				      v4l2ToDrm(arg->fmt.pix.pixelformat),
+				      bufferCount_);
 	if (ret < 0)
 		return -EINVAL;