backend-fbdev: more into new subdir

For consistency with other backends.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
2 jobs for mr/move-backends in 1 minute and 18 seconds (queued for 1 second)
Status Job ID Name Coverage
  Container Prep
passed #302526
container_prep

00:00:30

 
  Build
passed #302527
build-native-meson

00:00:47