[WATCHDOG] MAINTAINERS: remove ZF MACHZ WATCHDOG entry

- maintainer has not been active for years
- maintainer email bounces
- URL no longer exists
- covered by the WATCHDOG DEVICE DRIVERS entry

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>