dmaengine: qcom: bam_dma: fix kernel-doc style for tasklet

Commit 00c4747a ("dmaengine: qcom: 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: 00c4747a

 ("dmaengine: qcom: convert tasklets to use new tasklet_setup() API")
Link: https://lore.kernel.org/r/20201007083113.567559-3-vkoul@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>