iio: at91_adc: Cocci spatch "noderef"

sizeof when applied to a pointer typed expression gives the size of the
pointer.
Found by coccinelle spatch "misc/noderef.cocci"
Signed-off-by: NThomas Meyer <thomas@m3y3r.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/adc/at91_adc.c

@@ -279,7 +279,7 @@ static int at91_adc_trigger_init(struct iio_dev *idev)
 	int i, ret;
 
 	st->trig = devm_kzalloc(&idev->dev,
-				st->trigger_number * sizeof(st->trig),
+				st->trigger_number * sizeof(*st->trig),
 				GFP_KERNEL);
 
 	if (st->trig == NULL) {