drm/syncobj: flatten dma_fence_chains on transfer

It is illegal to add a dma_fence_chain as timeline point. Flatten out
the fences into a dma_fence_array instead.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Nirmoy Das <nirmoy.das@linux.intel.com>
Cc: <stable@vger.kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220209182600.434803-1-christian.koenig@amd.com