mx31/mx35/mx51/mx53/mx6: add watchdog

Use a common watchdog driver for all these cpus.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/include/configs/mx31pdk.h b/include/configs/mx31pdk.h
index 138a941..34e4295 100644
--- a/include/configs/mx31pdk.h
+++ b/include/configs/mx31pdk.h
@@ -61,6 +61,7 @@
 #define CONFIG_MXC_UART
 #define CONFIG_MXC_UART_BASE	UART1_BASE
 #define CONFIG_HW_WATCHDOG
+#define CONFIG_IMX_WATCHDOG
 #define CONFIG_MXC_GPIO
 
 #define CONFIG_HARD_SPI