drivers/rtc/rtc-ds1742.c: add devicetree support

This patch allows the driver to be enabled with devicetree.
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/devicetree/bindings/rtc/maxim,ds1742.txt

+* Maxim (Dallas) DS1742/DS1743 Real Time Clock
+
+Required properties:
+- compatible: Should contain "maxim,ds1742".
+- reg: Physical base address of the RTC and length of memory
+  mapped region.
+
+Example:
+	rtc: rtc@10000000 {
+		compatible = "maxim,ds1742";
+		reg = <0x10000000 0x800>;
+	};

drivers/rtc/rtc-ds1742.c

@@ -13,12 +13,13 @@
  */
 
 #include <linux/bcd.h>
-#include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/gfp.h>
 #include <linux/delay.h>
 #include <linux/jiffies.h>
 #include <linux/rtc.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -215,12 +216,19 @@ static int ds1742_rtc_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static struct of_device_id __maybe_unused ds1742_rtc_of_match[] = {
+	{ .compatible = "maxim,ds1742", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ds1742_rtc_of_match);
+
 static struct platform_driver ds1742_rtc_driver = {
 	.probe		= ds1742_rtc_probe,
 	.remove		= ds1742_rtc_remove,
 	.driver		= {
 		.name	= "rtc-ds1742",
 		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(ds1742_rtc_of_match),
 	},
 };