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/mach-at91/spl_atmel.c b/arch/arm/mach-at91/spl_atmel.c
index 597ff8c..ef745c9 100644
--- a/arch/arm/mach-at91/spl_atmel.c
+++ b/arch/arm/mach-at91/spl_atmel.c
@@ -98,7 +98,7 @@
 	configure_2nd_sram_as_l2_cache();
 #endif
 
-#if !defined(CONFIG_AT91SAM9_WATCHDOG)
+#if !defined(CONFIG_WDT_AT91)
 	/* disable watchdog */
 	at91_disable_wdt();
 #endif