freedreno/drm: Fix potential bo cache vs export crash
Keep the list head valid (empty) after allocation from bo cache. Avoids a potential later crash in lookup_bo in the following sequence: 1. alloc, bo cache hit 2. export 3. re-import Cc: mesa-stable Fixes: f3cc0d27 ("freedreno: import libdrm_freedreno + redesign submit") Closes: mesa/mesa#6988 Signed-off-by:Rob Clark <robdclark@chromium.org> Part-of: <mesa/mesa!17888> (cherry picked from commit 8b3f2a9e)