dmaengine: sun6i: fix the uninitialized value for v_lli

dma_pool_alloc does not initialize the value of the newly allocated
block for the v_lli, and the uninitilize value make the tests failed
which is on pine64 with dmatest.
we can fix it just change the "|=" to "=" for the v_lli->cfg.

Signed-off-by: Hao Zhang <hao5781286@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>