drm/xe/sync: Fix user fence leak on alloc failure

In the Linux kernel, the following vulnerability has been resolved: drm/xe/sync: Fix user fence leak on alloc failure When dma_fence_chain_alloc() fails, properly release the user fence reference to prevent a memory leak. (cherry picked from commit a5d5634cde48a9fcd68c8504aa07f89f175074a0)