dmaengine: sf-pdma: remove unused 'desc'

'desc' variable is now defined but not used in sf_pdma_donebh_tasklet(),
causing this warning:

drivers/dma/sf-pdma/sf-pdma.c: In function 'sf_pdma_donebh_tasklet':
drivers/dma/sf-pdma/sf-pdma.c:287:23: warning: unused variable 'desc' [-Wunused-variable]

Remove this unused variable

Reported-by: Stephen Rothwell <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/sf-pdma/sf-pdma.c

···
 static void sf_pdma_donebh_tasklet(unsigned long arg)
 {
 	struct sf_pdma_chan *chan = (struct sf_pdma_chan *)arg;
-	struct sf_pdma_desc *desc = chan->desc;
 	unsigned long flags;
 
 	spin_lock_irqsave(&chan->lock, flags);