rtc: ab8500: Add a sentinel to ab85xx_rtc_ids[]

Add a sentinel to ab85xx_rtc_ids[] in order to fix the following error:

drivers/rtc/rtc-ab8500: struct platform_device_id is 24 bytes.  The last of 2 is:
0x61 0x62 0x38 0x35 0x34 0x30 0x2d 0x72 0x74 0x63 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x8c
FATAL: drivers/rtc/rtc-ab8500: struct platform_device_id is not terminated with a NULL entry!
Reported-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Reported-by: Olof's autobuilder <build@lixom.net>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-ab8500.c

@@ -445,6 +445,7 @@ static const struct rtc_class_ops ab8540_rtc_ops = {
 static const struct platform_device_id ab85xx_rtc_ids[] = {
 	{ "ab8500-rtc", (kernel_ulong_t)&ab8500_rtc_ops, },
 	{ "ab8540-rtc", (kernel_ulong_t)&ab8540_rtc_ops, },
+	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(platform, ab85xx_rtc_ids);