dma-buf: Enable signaling on fence for selftests

Here's enabling software signaling on fence for selftest.

Signed-off-by: Arvind Yadav <Arvind.Yadav@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220914164321.2156-4-Arvind.Yadav@amd.com


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