dmaengine: at_xdmac: fix bug in prep_dma_cyclic

In cyclic mode, the round chaining has been broken by the introduction
of at_xdmac_queue_desc(): AT_XDMAC_MBR_UBC_NDE is set for all descriptors
excepted for the last one. at_xdmac_queue_desc() has to be called one
more time to chain the last and the first descriptors.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Fixes: 0d0ee751 ("dmaengine: xdmac: Rework the chaining logic")
Signed-off-by: Vinod Koul <vinod.koul@intel.com>