dma-buf/dma-fence: Remove return code of signaling-functions

dma-buf/dma-fence: Remove return code of signaling-functions

All functions used for signaling a fence return an error code whose sole
purpose is to tell whether a fence was already signaled.

This is racy and has been used by almost no party in the kernel, and the
few users have been removed in preceding cleanup commits.

Turn all signaling-functions into void-functions.

Suggested-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20251201105011.19386-9-phasta@kernel.org