watchdog: Add a driver for the sunxi watchdog

This driver supports the sun4i/sun6i/sun20i watchdog timers.
They have a maximum timeout of 16 seconds.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 7d2d6ea..d306054 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -27,6 +27,7 @@
 	default 128000 if ARCH_MX31 || ARCH_MX5 || ARCH_MX6
 	default 128000 if ARCH_MX7 || ARCH_VF610
 	default 30000 if ARCH_SOCFPGA
+	default 16000 if ARCH_SUNXI
 	default 60000
 	help
 	  Watchdog timeout in msec
@@ -270,6 +271,13 @@
 	  Enable the STM32 watchdog (IWDG) driver. Enable support to
 	  configure STM32's on-SoC watchdog.
 
+config WDT_SUNXI
+	bool "Allwinner sunxi watchdog timer support"
+	depends on WDT && ARCH_SUNXI
+	default y
+	help
+	  Enable support for the watchdog timer in Allwinner sunxi SoCs.
+
 config XILINX_TB_WATCHDOG
 	bool "Xilinx Axi watchdog timer support"
 	depends on WDT