drm/scheduler: use new iterator in drm_sched_job_add_implicit_dependencies v2

Simplifying the code a bit.

v2: use dma_resv_for_each_fence

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-17-christian.koenig@amd.com