It's not allowed to nest another dma_fence container into a dma_fence_array
or otherwise we can run into recursion.

Warn about that when we create a dma_fence_array.

v2: fix comment style and typo in the warning pointed out by Thomas
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204100429.2049-3-christian.koenig@amd.com