power: supply: cpcap-battery: fix invalid usage of list cursor

Fix invalid usage of a list_for_each_entry in cpcap_battery_irq_thread().
Empty list or fully traversed list points to list head, which is not
NULL (and before the first element containing real data).
Signed-off-by: Guangqing Zhu <zhuguangqing83@gmail.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Carl Philipp Klemm <philipp@uvos.xyz>
Tested-by: Carl Philipp Klemm <philipp@uvos.xyz>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/cpcap-battery.c

@@ -786,7 +786,7 @@ static irqreturn_t cpcap_battery_irq_thread(int irq, void *data)
 			break;
 	}
 
-	if (!d)
+	if (list_entry_is_head(d, &ddata->irq_list, node))
 		return IRQ_NONE;
 
 	latest = cpcap_battery_latest(ddata);