MAINTAINERS: Add watchdog maintainers entry

I've been handling "inofficially" the watchdog related patches for a few
years now. Let's make this official and add a tree for it and also add
myself here in the MAINTAINERS file.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Cc: Harald Seiler <hws@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 0f39bc6..82fc49e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1326,6 +1326,14 @@
 F:	test/dm/virtio.c
 F:	doc/develop/driver-model/virtio.rst
 
+WATCHDOG
+M:	Stefan Roese <sr@denx.de>
+S:	Maintained
+T:	git https://source.denx.de/u-boot/custodians/u-boot-watchdog.git
+F:	cmd/wdt.c
+F:	drivers/watchdog/
+F:	include/watchdog*.h
+
 X86
 M:	Simon Glass <sjg@chromium.org>
 M:	Bin Meng <bmeng.cn@gmail.com>