sunxi: Enable watchdog timer support by default

A watchdog helps recover from hangs or failure to boot an OS. It can
also be used by the sysreset framework to intentionally reset the
system. Now that a driver is available, let's enable this functionality
on sunxi boards.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ebd9468..02f8306 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1066,6 +1066,7 @@
 	imply SPL_POWER
 	imply SPL_SERIAL
 	imply USB_GADGET
+	imply WDT
 
 config ARCH_U8500
 	bool "ST-Ericsson U8500 Series"