dma-buf: fix dma_resv_test_signaled test_all handling v2

As the name implies if testing all fences is requested we
should indeed test all fences and not skip the exclusive
one because we see shared ones.

v2: fix logic once more

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210702111642.17259-3-christian.koenig@amd.com