watchdog: ftwdt010: return a previously deleted driver now ported to DM

The ftwdt010 watchdog driver was deleted by
commit 11232139e399 ("nds32: Remove the architecture")

Return it to the codebase in a DM compatible form. Enable it in
sandbox_defconfig to test compilability.
Another platform using ftwdt010 will be submitted later.

Signed-off-by: Sergei Antonov <saproj@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index f999159..fd795b2 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -27,6 +27,7 @@
 obj-$(CONFIG_WDT_CORTINA) += cortina_wdt.o
 obj-$(CONFIG_WDT_ORION) += orion_wdt.o
 obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o
+obj-$(CONFIG_WDT_FTWDT010) += ftwdt010_wdt.o
 obj-$(CONFIG_WDT_GPIO) += gpio_wdt.o
 obj-$(CONFIG_WDT_MAX6370) += max6370_wdt.o
 obj-$(CONFIG_WDT_MESON_GXBB) += meson_gxbb_wdt.o