ALSA: dummy: Use DIV_ROUND_UP() instead of open-coding it

Use DIV_ROUND_UP() instead of open-coding it. This documents intent
and makes it more clear what is going on for the casual reviewer.

Generated using the following the Coccinelle semantic patch.

// <smpl>
@@
expression x, y;
@@
-(((x) + (y) - 1) / (y))
+DIV_ROUND_UP(x, y)
// </smpl>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20201223172229.781-7-lars@metafoo.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/drivers/dummy.c

@@ -236,7 +236,7 @@ struct dummy_systimer_pcm {
 static void dummy_systimer_rearm(struct dummy_systimer_pcm *dpcm)
 {
 	mod_timer(&dpcm->timer, jiffies +
-		(dpcm->frac_period_rest + dpcm->rate - 1) / dpcm->rate);
+		DIV_ROUND_UP(dpcm->frac_period_rest, dpcm->rate));
 }
 
 static void dummy_systimer_update(struct dummy_systimer_pcm *dpcm)