dma-buf/dma-fence: Add dma_fence_check_and_signal()

dma-buf/dma-fence: Add dma_fence_check_and_signal()

The overwhelming majority of users of dma_fence signaling functions
don't care about whether the fence had already been signaled by someone
else. Therefore, the return code shall be removed from those functions.

For the few users who rely on the check, a new, specialized function
shall be provided.

Add dma_fence_check_and_signal(), which signals a fence if it had not
yet been signaled, and informs the user about that.

Add a counter part, dma_fence_check_and_signal_locked(), which doesn't
take the spinlock.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20251201105011.19386-4-phasta@kernel.org