dmaengine: altera-msgdma: fix kernel-doc style for tasklet

Commit 6752e40d ("dmaengine: altera-msgdma: convert tasklets to use
new tasklet_setup() API") updated driver to use new tasklet_setup() API
but missed to update the documentation for the tasklet function.

Fixes: 6752e40d ("dmaengine: altera-msgdma: convert tasklets to use new tasklet_setup() API")
Link: https://lore.kernel.org/r/20201007083113.567559-2-vkoul@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>