dmaengine: at_hdmac: remove unused function

commit 54f8d501e8428 ('dmaengine: remove DMA unmap from drivers')
refactored some code which resulted in an unused function in the at_hdmac
driver:

drivers/dma/at_hdmac_regs.h:350:23: warning: 'chan2parent' defined but
not used [-Wunused-function]

Fixes: 54f8d501e8428 ('dmaengine: remove DMA unmap from drivers')
Signed-off-by: Olof Johansson <[e-mail]>
Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
Acked-by: Nicolas Ferre <[e-mail]>
Acked-by: Bartlomiej Zolnierkiewicz <[e-mail]>
Acked-by: Vinod Koul <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>

drivers/dma/at_hdmac_regs.h

···
 {
 	return &chan->dev->device;
 }
-static struct device *chan2parent(struct dma_chan *chan)
-{
-	return chan->dev->device.parent;
-}
 
 #if defined(VERBOSE_DEBUG)
 static void vdbg_dump_regs(struct at_dma_chan *atchan)