dma-buf: Use dma_fence_unwrap_for_each when importing fences

Ever since 68129f43 ("dma-buf: warn about containers in dma_resv object"),
dma_resv_add_shared_fence will warn if you attempt to add a container fence.
While most drivers were fine, fences can also be added to a dma_resv via the
recently added DMA_BUF_IOCTL_IMPORT_SYNC_FILE.  Use dma_fence_unwrap_for_each
to add each fence one at a time.

Fixes: 59474049

 ("dma-buf: Add an API for importing sync files (v10)")
Signed-off-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Reported-by: Sarah Walker <Sarah.Walker@imgtec.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
CC: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220802210158.4162525-1-jason.ekstrand@collabora.com
Signed-off-by: Christian König <christian.koenig@amd.com>