dmaengine: sprd: Support DMA link-list cyclic callback

The Spreadtrum DMA link-list mode is always one cyclic transfer,
so we should clear the SPRD_DMA_LLIST_END flag for the link-list
configuration. Moreover add cyclic callback support for the cyclic
transfer.

Signed-off-by: Eric Long <eric.long@spreadtrum.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>