When using direct DMABuf upload, supported DRM formats and modifiers
pairs should be translated to RGBA. Instead of overwriting the translation
to RGBA, which may endup having nothing to override, we introduce a new
flag for the transform helper, so it can do direct translation.
This fixes a regression introduced by !9306, and fixes more negotiations
issues.
Fixes#4525
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9339>
d45864d77c