libweston/backend-drm: Re-order gbm destruction at DRM-backend tear down

Tearing down the drm-backend when there are no input devices, would call for the gbm device destruction before compositor shutdown. The latter would call into the renderer detroy function and assume that the EGLDisplay, which was created using the before-mentioned gbm device, is still available. This patch re-orders the gbm destruction after the compositor shutdown when no one would make use of it.

Fixes: #314 (closed)

Signed-off-by: Marius Vlad marius.vlad@collabora.com Suggested-by: Daniel Stone daniel.stone@collabora.com