dm: watchdog: add BCM6345 watchdog driver

This driver is a simplified version of linux/drivers/watchdog/bcm63xx_wdt.c

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 8378601..4b19e4c 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -18,4 +18,5 @@
 obj-$(CONFIG_WDT) += wdt-uclass.o
 obj-$(CONFIG_WDT_SANDBOX) += sandbox_wdt.o
 obj-$(CONFIG_WDT_ASPEED) += ast_wdt.o
+obj-$(CONFIG_WDT_BCM6345) += bcm6345_wdt.o
 obj-$(CONFIG_BCM2835_WDT)       += bcm2835_wdt.o