dma-fence: Signal all callbacks from dma_fence_release()

This is an illegal scenario, to free the fence whilst there are pending
callbacks. Currently, we emit a WARN and then cast aside the callbacks
leaving them dangling. Alternatively, we could set an error on the fence
and then signal fence so that any dependency chains from the fence can
be tidied up, and if they care they can check for the error.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190609110002.31915-1-chris@chris-wilson.co.uk