rtc/spear: add Device Tree probing capability

SPEAr platforms now support DT and so must convert all drivers support DT.
This patch adds DT probing support for rtc and updates its documentation
too.
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Rajeev Kumar <rajeev-dlh.kumar@st.com>
Cc: Rob Herring <robherring2@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/devicetree/bindings/rtc/spear-rtc.txt

+* SPEAr RTC
+
+Required properties:
+- compatible : "st,spear600-rtc"
+- reg : Address range of the rtc registers
+- interrupt-parent: Should be the phandle for the interrupt controller
+  that services interrupts for this device
+- interrupt: Should contain the rtc interrupt number
+
+Example:
+
+	rtc@fc000000 {
+		compatible = "st,spear600-rtc";
+		reg = <0xfc000000 0x1000>;
+		interrupt-parent = <&vic1>;
+		interrupts = <12>;
+	};

drivers/rtc/rtc-spear.c

@@ -16,6 +16,7 @@
 #include <linux/io.h>
 #include <linux/irq.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/rtc.h>
 #include <linux/slab.h>
@@ -519,6 +520,14 @@ static void spear_rtc_shutdown(struct platform_device *pdev)
 	clk_disable(config->clk);
 }
 
+#ifdef CONFIG_OF
+static const struct of_device_id spear_rtc_id_table[] = {
+	{ .compatible = "st,spear600-rtc" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, spear_rtc_id_table);
+#endif
+
 static struct platform_driver spear_rtc_driver = {
 	.probe = spear_rtc_probe,
 	.remove = __devexit_p(spear_rtc_remove),
@@ -527,6 +536,7 @@ static struct platform_driver spear_rtc_driver = {
 	.shutdown = spear_rtc_shutdown,
 	.driver = {
 		.name = "rtc-spear",
+		.of_match_table = of_match_ptr(spear_rtc_id_table),
 	},
 };