rtc: abx80x: fix RTC write bit

Fix RTC write bit as per application manual

Cc: stable@vger.kernel.org # 4.1+
Signed-off-by: NMitja Spes <mitja@lxnav.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-abx80x.c

@@ -28,7 +28,7 @@
 #define ABX8XX_REG_WD		0x07
 
 #define ABX8XX_REG_CTRL1	0x10
-#define ABX8XX_CTRL_WRITE	BIT(1)
+#define ABX8XX_CTRL_WRITE	BIT(0)
 #define ABX8XX_CTRL_12_24	BIT(6)
 
 #define ABX8XX_REG_CFG_KEY	0x1f