dmaengine: axi-dmac: Add support for interleaved cyclic transfers

The DMAC HDL core supports interleaved & cyclic transfers.
An example use-case for this mode is when the controller is used as a
video DMA.

This change sets the `cyclic` field to true, so that when the IRQ comes and
the `axi_dmac_transfer_done()` callback is called (from the interrupt
handler) the proper `vchan_cyclic_callback()` is called. This way the
DMAEngine framework will process data correctly for interleaved + cyclic
transfers.

This doesn't fix anything. It's an enhancement to the driver.

Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>