dmaengine: at_xdmac: Remove a level of indentation in at_xdmac_tasklet()

Apart of making the code easier to read, this patch is a prerequisite for
a functional change: tasklets run with interrupts enabled, so we need to
protect atchan->irq_status with spin_lock_irq() otherwise the tasklet can
be interrupted by the IRQ that modifies irq_status. atchan->irq_status
will be protected in a further patch.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20211215110115.191749-12-tudor.ambarus@microchip.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>