arm: at91: wdt: Convert watchdog driver to dm/dt

Convert the Watchdog driver for AT91SAM9x processors to support
the driver model and device tree. Changes "CONFIG_AT91SAM9_WATCHDOG"
to new "CONFIG_WDT_AT91" Kconfig option.

Signed-off-by: Prasanthi Chellakumar <prasanthi.chellakumar@microchip.com>
diff --git a/arch/arm/dts/at91sam9260-smartweb.dts b/arch/arm/dts/at91sam9260-smartweb.dts
index e59781b..a22de2d 100644
--- a/arch/arm/dts/at91sam9260-smartweb.dts
+++ b/arch/arm/dts/at91sam9260-smartweb.dts
@@ -89,6 +89,7 @@
 			};
 
 			watchdog@fffffd40 {
+				timeout-sec = <15>;
 				status = "okay";
 			};
 
diff --git a/arch/arm/dts/at91sam9g20-taurus.dts b/arch/arm/dts/at91sam9g20-taurus.dts
index 7931c0a..cee228b 100644
--- a/arch/arm/dts/at91sam9g20-taurus.dts
+++ b/arch/arm/dts/at91sam9g20-taurus.dts
@@ -98,6 +98,7 @@
 			};
 
 			watchdog@fffffd40 {
+				timeout-sec = <15>;
 				status = "okay";
 			};