v4l2object: Update image size when extrapolating

Update the image size according the amount of data we are going to
read/write. This workaround bugs in driver where the sizeimage provided
by TRY/S_FMT represent the buffer length (maximum size) rather then the expected
bytesused (buffer size).

https://bugzilla.gnome.org/show_bug.cgi?id=775564
1 file changed