dmaengine: omap: Support for element mode in cyclic DMA

When src_maxburst/dst_maxburst is set to 0 by the users of cyclic DMA
(mostly audio) indicates that we should configure the omap DMA to element
sync mode instead of packet mode.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Vinod Koul <vinod.koul@linux.intel.com>
Tested-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>