anv: properly handle fence import of sync_fd = -1
Signed-off-by:Lionel Landwerlin <lionel.g.landwerlin@intel.com> Fixes: 43e8808b ("anv: Add support for the SYNC_FD handle type for fences") Reviewed-by:
Tapani Pälli <tapani.palli@intel.com> Part-of: <!5964> (cherry picked from commit 3a4024e7)