dma-buf: fix dma_fence_array_signaled v4

The function silently assumed that signaling was already enabled for the
dma_fence_array. This meant that without enabling signaling first we would
never see forward progress.

Fix that by falling back to testing each individual fence when signaling
isn't enabled yet.

v2: add the comment suggested by Boris why this is done this way
v3: fix the underflow pointed out by Tvrtko
v4: atomic_read_acquire() as suggested by Tvrtko

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Tested-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12094
Cc: <stable@vger.kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241112121925.18464-1-christian.koenig@amd.com