drm/syncobj: reject invalid flags in drm_syncobj_find_fence

The only flag that is meaningful to drm_syncobj_find_fence is
DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT. It should return -EINVAL for any
other flag bits.

Signed-off-by: Erik Kurzinger <ekurzinger@nvidia.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20240119163208.3723457-2-ekurzinger@nvidia.com