dmaengine: sirf: off by one in of_dma_sirfsoc_xlate()

The ">" here should be ">=" or we are one step beyond the end of the
sdma->channels[] array.

Fixes: 2e041c94

 ('dmaengine: sirf: enable generic dt binding for dma channels')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>