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/configs/smartweb_defconfig b/configs/smartweb_defconfig
index cf6f275..e9c2b63 100644
--- a/configs/smartweb_defconfig
+++ b/configs/smartweb_defconfig
@@ -59,3 +59,6 @@
 CONFIG_USB_ETHER_MCS7830=y
 CONFIG_SPL_TINY_MEMSET=y
 # CONFIG_EFI_LOADER is not set
+CONFIG_WDT=y
+CONFIG_WDT_AT91=y
+CONFIG_AT91_HW_WDT_TIMEOUT=y