mfd: act8945a: Add .of_compatible for act8945a-charger

To regard the act8945a-charger as a sub-device, add .of_compatible for
act8945a-charger cell.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/act8945a.c b/drivers/mfd/act8945a.c
index 10c6d2d..a4024d9 100644
--- a/drivers/mfd/act8945a.c
+++ b/drivers/mfd/act8945a.c
@@ -23,6 +23,7 @@
 	},
 	{
 		.name = "act8945a-charger",
+		.of_compatible = "active-semi,act8945a-charger",
 	},
 };