UPSTREAM: dma-buf/sync_file: cleanup fence merging a bit

krealloc_array() ignores attempts to reduce the array size, so the attempt
to save memory is completely pointless here.

Also move testing for the no fence case into sync_file_set_fence(), this
way we don't even touch the fence array when we don't have any fences.

Change-Id: Ibecc33d218935c246c4bb64509a1fadece47b16d
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220426124637.329764-1-christian.koenig@amd.com


(cherry picked from commit f778f405)
Bug: 394776841
Bug: 397845301
Signed-off-by: T.J. Mercier <tjmercier@google.com>