Instead return the fence directly. Avoids memory allocation to store the
fence.

v2: cleanup coding style as well

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014084641.128280-6-christian.koenig@amd.com