watchdog: add amlogic watchdog support

Add support for hardware watchdog timer for Amlogic SoCs.
This driver has been heavily inspired by his Linux equivalent
(meson_gxbb_wdt.c).

Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>

Signed-off-by: Philippe Boos <pboos@baylibre.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index c51d3b1..50e6a1e 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -175,6 +175,13 @@
 	help
 	  Select this to enable max6370 watchdog timer.
 
+config WDT_MESON_GXBB
+	bool "Amlogic watchdog timer support"
+	depends on WDT
+	help
+	  Select this to enable Meson watchdog timer,
+	  which can be found on some Amlogic platforms.
+
 config WDT_MPC8xx
 	bool "MPC8xx watchdog timer support"
 	depends on WDT && MPC8xx