linux-imx

dmaengine: virt-dma: Fix kernel-doc annotations

In kernel-doc annotations parameters need to start with a @ for them to be
properly recognized. Add those where missing for virt-dma.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>