dmaengine: jz4780: fix resource leaks on error exit return

In two cases when jz4780_dma_setup_hwdesc fails, there is a memory
leak on the allocated desc and associated DMA pools on the error
exit return path.  Fix this by free'ing the resources before
returning.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>