When the driver does not implement ENUM_FRMESIZE for some specific
formats, the caps limiting the sizes may endup empty, which results in
assuming the driver can scale to any sizes.
Ensure that the original size is in the caps to prevent this assumption.
This happens with Hantro drive, since it only reply to that call if the
format is postprocessed.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7849>