net: ethernet: ti: davinci_cpdma: correct check on NULL in set rate

Check "ch" on NULL first, then get ctlr.

Signed-off-by: Ivan Khoronzhuk <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/ti/davinci_cpdma.c

···
  */
 int cpdma_chan_set_rate(struct cpdma_chan *ch, u32 rate)
 {
-	struct cpdma_ctlr *ctlr = ch->ctlr;
 	unsigned long flags, ch_flags;
+	struct cpdma_ctlr *ctlr;
 	int ret, prio_mode;
 	u32 rmask;
 
···
 	if (ch->rate == rate)
 		return rate;
 
+	ctlr = ch->ctlr;
 	spin_lock_irqsave(&ctlr->lock, flags);
 	spin_lock_irqsave(&ch->lock, ch_flags);