drm/nouveau: Simplify calls to nvif_event_block()

nouveau_fence_signal() returns a de-facto boolean to indicate when
nvif_event_block() shall be called.

The code can be made more compact and readable by calling
nvif_event_block() in nouveau_fence_update() directly.

Make those calls in nouveau_fence.c more canonical.

Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20250424130254.42046-4-phasta@kernel.org


Signed-off-by: Danilo Krummrich <dakr@kernel.org>