Philipp Zabel authored Mar 22, 2021 and Derek Foreman committed Sep 28, 2023

Insert the backend into the weston_compositor::backend_list instead
of setting weston_compositor::backend. The compositor uses this to
determine whether the backend is capable of being loaded simultaneously
with other backends.

To stay backwards compatible, the RDP backend can be loaded as primary
backend. It also supports being loaded as secondary backend.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>