drm/i915: Fix i915_request fence wait semantics

The i915_request fence wait behaves differently for timeout = 0
compared to expected dma-fence behavior.

i915 behavior:
- Unsignaled: -ETIME
- Signaled: 0 (= timeout)

Expected:
- Unsignaled: 0
- Signaled: 1

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211116102431.198905-6-christian.koenig@amd.com


Signed-off-by: Christian König <christian.koenig@amd.com>